A-VoIP aṅko kiṃ hoti? Kasmā appā VoIP-aṅke paṭikkhipanti

You type a number into a sign-up form and the app answers with “This phone number can’t be used for verification” or “VoIP numbers are not supported.” No code, no explanation. The app looked the number up before sending anything, and did not like what it found.

The usual fix is a non-VoIP number: one that lookup databases list as a mobile line on a real carrier, rather than a number issued by an internet calling service. Here is what that difference means, how apps tell the two apart, and what to do when a number is turned away.

Aṅkānaṃ catasso jātiyo#

Mobile numbers belong to a SIM or eSIM on a carrier’s network. Getting one means going through a carrier and, in many countries, registering the SIM to a name.

Landlines are fixed lines at an address. Most cannot receive text messages at all, so they rarely work for SMS codes.

Fixed VoIP numbers come from internet phone services linked to a real address, such as a home phone bundled with broadband or an office system. Because they are tied to a customer and an address, some apps accept them. Others lump them in with every other VoIP line.

Non-fixed VoIP numbers are the ones apps worry about. Anyone can create one online in minutes, sometimes for free, with no address and no ID, and drop it just as fast.

Strictly speaking, landlines are non-VoIP too. Since they rarely receive SMS, a non-VoIP number in practice means a mobile number that reads as mobile when an app checks it.

Appā aṅkaṃ kathaṃ vīmaṃsanti#

Most of the checking happens in the second after you tap “Send code,” before any SMS leaves. Apps do not publish the exact rules. The checks usually fall into four groups.

Line type and carrier. Appo, vīmaṃsana-sevā vā yā payujati, aṅkaṃ aṅka-vidhi-bhāṇḍāgāresu ca vāhaka-bhāṇḍāgāresu gavesati. Paṭivacanaṃ raṭṭhena, vāhakena, lekhā-jātiyā ca paccāgacchati: mobile, thala-lekhā, VoIP vā. Ke ci esanā mobile-jālaṃ pi pucchanti, aṅko sakammo udāhu na. Aṅkā vāhakānaṃ antaraṃ calanti, nīharaṇa-lekhā ca niccaṃ navā na honti, tasmā saccako mobile-aṅko kadāci micchā paṭhīyati. Khuddakānaṃ vāhakānañ ca puna-vikkayīnaṃ aṅkā pi kadāci na ekarūpena vaggīyanti. Phalaṃ VoIP ti vadati ce, bahū appā tattha yeva tiṭṭhanti.

Reputation. Risk-scoring services keep a history: how long the number has been active, how often it appears in sign-ups, and whether it has been linked to spam or fraud. A poor score can be refused even if the line is a genuine mobile number.

Reuse. The app also checks its own records. Has this number already verified an account? Many apps allow only one account per number, or refuse numbers they have seen too often in a short period.

Context. Some apps compare the number’s country with your IP address, device language or app-store region, and add extra steps when they do not line up.

Sometimes all of this passes and the SMS still never comes. The app’s SMS provider may filter certain routes, or the app may throttle repeated requests. From your side it looks just like a refusal.

Kasmā appā VoIP-aṅke paṭikkhipanti#

It is not really about the technology. It comes down to cost and accountability.

• They are cheap to create in bulk. Phone verification exists to make each new account cost something. If numbers can be generated by the hundred for next to nothing, the check stops working, so apps block the kinds of numbers that make that possible.
• They are easy to abandon. A number that can disappear tomorrow is a poor recovery channel.
• They are linked to abuse. Disposable numbers are a common tool for spam, fake reviews and promo abuse, so many risk systems treat VoIP as high risk by default.
• Every SMS costs the app money. Apps would rather not pay to verify lines that are likely to be thrown away.

The same logic catches any heavily shared number, VoIP or not. A genuine mobile number that many strangers have used on public inbox sites looks just as disposable. Free SMS sites versus a private number explains why.

Policies differ. Some apps accept VoIP, some block only the non-fixed kind, and rules change without notice. What passes today may not pass next month.

Aṅkaṃ kiṃ gahitaṃ karoti#

Numbers that get codes through tend to share a few traits:

• They read as mobile in line-type lookups, on a carrier that operates in that country.
• They have a clean history with that app: not already attached to an account, and not part of a burst of recent sign-ups.
• They come from a country the app serves, ideally one that fits the rest of the account.
• They sit on a route the app’s SMS provider delivers to, which you learn by testing, or from other people’s recent results.

No number is guaranteed to pass every app. Anyone who promises that is guessing.

SmsWays-aṅkā kattha anurūpā#

The numbers run on mobile networks in each country, not on VoIP ranges, which is why they usually pass the line-type checks that screen out internet calling numbers. Not every route is a SIM in a single handset. Some are resold lines on local mobile networks. Rentals make the distinction explicit:

• Physical SIM: a SIM in a real handset, the most widely accepted.
• Routed line: a number on a local network, cheaper, and fine for most services.
• Premium line: a SIM on a major carrier, for the strictest apps.

Lekhā-jāti paṭhamo yeva paligho hoti. Upakāra-saññā dāna-pamāṇaṃ hoti. Appañ ca raṭṭhaṃ vicitvā ekekaṃ jālaṃ cattāro daṇḍe dasseti: pacchimānaṃ āṇānaṃ bhāgo yattha saṅketo āgato. Payoge so eko aṅko esanā, yasa-pamāṇāni, puna-payoga-mariyādā ca ekato dasseti. Ekakālikaṃ mūlaṃ vetanaṃ hoti SMS āgacchate yeva, tasmā paṭikkhittaṃ jālaṃ vīmaṃsituṃ thokāni minuṭṭāni harati, na dhanaṃ.

If this is new, receiving SMS online without a SIM walks through the whole process.

Aṅko paṭikkhitto ce kiṃ kātabbaṃ#

The error usually tells you which check failed. Wording varies, but most messages fall into four patterns.

• “Invalid phone number.” Usually a format problem. Select the country code once in the app’s list, and do not type it again.
• “This number can’t be used” or “not supported.” A line-type or reputation refusal. Try another network.
• “Already in use” or “used too many times.” The app’s reuse limit. Take a fresh number, ideally from another network.
• “Too many attempts.” A limit on the device or the connection, not on the number. Wait before trying again, or even a good number will fail.

When an app refuses a number before sending anything, nothing arrives and a one-time order is not charged. From there:

1. Change networks. Cancel after 2 minutes and pick another network in the same country, ideally one with more bars.
2. Change countries if every network there fails. Some apps are stricter with certain countries.
3. Go physical for strict apps. Rent a physical SIM or a premium line. They tend to pass more checks, and the number stays yours for later logins. Renting versus a one-time number helps you choose before you start.

If the number is accepted but no code comes, give it a minute or two. If the app switches to a voice call, pick SMS. These numbers receive text only. Still nothing? Cancel and change networks. Why SMS codes do not arrive covers the other causes.

A number that passes these checks is meant to keep your own number private, not to get around a ban an app placed on you. The anuññāta-payojana-nīti has the details.

Next step: open the ujjālana-paṭo, pick the app and the country, and compare the delivery bars before you choose a network.