#9 on the India communication chart: a zero-rating caller ID app with 38k installs a day, driven by ad-spend switches

On Nov 6, TrustCall: Caller ID & Blocker ranked #9 on India's Google Play free Communication chart. It had only been listed three months earlier, its developer site showed just one line, "Under Construction," its store page had zero ratings, and that day it got 38k installs. It isn't a new product; it's a worn-out caller ID template. It worked because of when the spend started, when it stopped, and which countries it targeted. Below we break down how this playbook adds up, who else is competing with it, and whether you should get in.

Its neighbors on the chart

On India's Communication free chart on 11-06, Truecaller is #3, a "Call Blocker: Caller ID, SMS" app from developer Nonari Tec that launched in Sep 11 sits at #7, and TrustCall is #9. Two newly launched look-alikes are sitting in the top ten, and they look almost identical.

TrustCall's developer is A CUBED. The site acubed.space shows only "Kim Yen Nguyen 2025" and "Under Construction." The privacy policy sits on a Google Sites page, and the contact is a personal Gmail. Going by the name, it's probably a Vietnamese individual or tiny studio (inference). The same developer account also published a short-drama app, "Short Drama: Short Story Reel," in Jun 18. It reached 1.27M installs, then fell off the charts by November, with daily adds dropping from 14k to 4 thousand. With the drama line cooling, they switched to caller ID: launched Jul 25, version 1.0.2, last updated Sep 25.

What it is

A replacement for the system phone app, all-in-one: caller ID, block list, dialer, contacts, SMS, and call log, all in one app. The store copy is careful: "view available information about incoming calls," saying only "available" information. The description never mentions a number database. Most likely it checks your contacts against numbers and adds a blocklist you maintain yourself (inference). What actually identifies strangers' numbers is a database built from hundreds of millions of users, as Truecaller has. This app doesn't have one.

Free, with ads, no in-app purchases, no subscriptions (Google Play store page, identical every day from 10-29 to 11-06). The only revenue is from ads.

The install curve looks like a switch

Plot its cumulative installs since launch and the shape is a square wave: a steep climb, a flat line, then another steep climb.

Source: Google Play install counts. 10-29 and earlier are estimates from the third-party AppstoreSpy; from 10-29 on, they're daily direct readings, and the two agree.

During the pause, adds were single digits a day. A real app with word of mouth and search doesn't drop to zero like that. The most likely explanation: nearly all installs were bought, the money stopped, and the volume stopped with it (inference, high confidence). Tens of thousands of installs a day with no ratings and no reviews point to the same conclusion.

The charts show it more clearly. 10-29 it only ranked #100–180 in Communication in four stores: UAE, Malaysia, India, and Saudi Arabia. A week later, by 11-06, it had charted in 22 countries: #9 in India, #16 in the UAE, #26 in Saudi Arabia, #48 in Malaysia, #62 in the Philippines, and #138 on India's overall free chart for all apps. Testing in three or four small markets, then expanding to two dozen countries once the numbers work, is the standard scale-up pattern.

Where users come from

• Paid acquisition, most likely Google's app ads (App Campaigns) plus cross-promotion across the AdMob network. The countries it spent in match the countries where it charted. Which networks, and how much, can't be found from outside, so it's unverified.
• Search-term piggybacking. The title is "TrustCall: Caller ID & Blocker," the package name is trustcall.callerid.spamblocker, and it differs from Truecaller by only a few letters. It stacks the big terms "caller id," "call blocker," and "spam." In India, huge numbers of people search for Truecaller, and a one-letter typo still catches traffic.
• Chart-driven volume. Once it climbs into India's Communication top ten, the chart itself brings some organic exposure. That's the point of pushing into category charts in emerging markets.
• Creators and influencers: none. A TikTok search for "trustcall caller id" turns up no relevant videos. X shows zero discussion in the past two months. The only places it appears online are auto-generated chart pages like APKPure and appfigures. Most "Trust Call" results on YouTube and Softonic are other apps with the same name.

Where the money comes from: the screen after a call

The reason this category of replacement-dialer apps gets built in batches sits in one spot: the screen that pops up when each call ends. Once the app becomes the default phone app, every call you finish can bring up a "call details" screen with an ad underneath. A person makes a few calls a day, so they see the ad several times, far more than a typical utility app that gets opened once or twice a day. Truecaller has this screen too. We didn't install TrustCall to check where it places its ads, so that's unverified.

An Android install in India typically costs a few cents (estimate). The whole business model is using ad revenue from this post-call screen to cover those few cents of acquisition cost. Whether it actually breaks even only the developer knows.

There's one more thing to know: this July, the ad-verification firm DoubleVerify singled out "AfterCall ads" as a new ad-fraud technique, and Malwarebytes and Cybernews both reported on it in late July. Their main targets were alarm and calendar apps, unrelated to phone calls, that trick users into granting "display over other apps" permission and then show full-screen ads after calls. Caller ID apps have a more legitimate reason to show a post-call screen. But once advertisers, ad networks, and Google Play tighten up, the price of this screen will be the first thing hit.

Who it's competing with

Caller ID is one of the oldest and most crowded categories on Google Play. Counting apps with caller / call block / spam in the name that launched after May, there are 38, with about 2.56M combined installs over the past 7 days (Google Play install counts, 11-06).

On this table, TrustCall shows no product difference at all. Features, naming, screenshots, and monetization match a dozen-plus apps from the same batch. Its only distinguishing factors are when it started buying installs and in which countries. It's also a copycat itself: two earlier apps called "Trust Call" already reached over ten million installs.

How many people know about it

Almost nobody knows about this app. No press coverage, no founder posting revenue, no one discussing it on X. But this path is already packed. Between 8 and October, five or six apps with "Trust Call" or "Trusted Call" in the name launched in the same window, and one of them is backed by a large Vietnamese publisher. In this business, the winner is whoever buys installs most precisely, not whoever builds the best product.

If it were you

The verdict: You can learn a clean "template plus pulse-spend" playbook from this. But copying it means joining a queue of dozens of apps, and the monetization point that matters most is now under scrutiny. Not a good deal.

Who it suits: A small studio already running paid campaigns for Android utility apps, with an AdMob account and an ROAS model in hand, treating this as one more category for its template library. Or someone holding real data on spam numbers in a specific country (carriers, anti-fraud partners, local communities), building the part that's missing: actually identifying strangers' numbers.

Who it doesn't suit: Indie developers who haven't run ads and are relying on organic store traffic. This curve already shows that when the spend stops, volume goes to zero. It's also a poor fit for anyone hoping to earn from subscriptions. Willingness to pay at this layer is low, and the position of identifying strangers' numbers while charging subscriptions is already taken by Truecaller.

How to do it: If you must enter, don't build the 39th "Trust Call." Pick a country where Truecaller's number database has weak coverage and local spam calls are common. Make local number data the selling point (for example, locally common scam number ranges or loan-collection numbers). On the post-call screen, show genuinely useful information like "this number has been flagged by N people," with ads placed lower. There's no technical barrier; templates are everywhere. The hard part is the number data, and whether the ad account math works.

How to acquire users: Copy its rhythm. Test with small budgets in 3–4 small countries, work out the cost per install and how much daily ad revenue the post-call screen brings in. Once the numbers work, expand to 20+ countries within a week, and put the core category keyword in the title. If you want organic volume for real, you need to build word of mouth through the number database. Paid acquisition can't replace that step.

Timing: There's no seasonal window, but there is a policy window. The post-call ad scrutiny started in July. If you want to test, do it over the next one to two quarters with small budgets, and don't bet big.

What would show this read is wrong: (1) Template apps like TrustCall and Nonari Tec keep running successive spend rounds after November, with shorter and shorter pauses. That would mean the math works and the bar is lower than it looks. (2) If Google Play or AdMob issues new rules targeting post-call ads and this batch of apps gets delisted or stops buying in bulk, the path is closed. (3) If a new local-number-database app grows steadily in one country without paid acquisition, that shows the "part they haven't built" is a real opportunity.

Data and sources: Google Play store page (gl=in, read 11-06); install counts and chart positions collected daily (10-29 to 11-06); earlier install counts are AppstoreSpy estimates; developer site acubed.space and the Google Play developer page; DoubleVerify Fraud Lab's report on AfterCall ads and coverage from Malwarebytes (2026-07-27) and Cybernews (2026-07-24); TikTok and X searches (11-06). Acquisition channels, spend, ad placements, and retention are all unverified.