Telegram is giving away FREE Premium subscriptions! All they need from you is to use your cell phone as a relay to text out their OTP codes! And the recipient of the OTP sees your phone number! What could POSSIBLY go wrong with this deal?
PLEASE don’t use Telegram! I personally recommend Matrix as it’s totally FOSS, you can self host, there are tons of front end clients to choose from. Or even use Signal. I have my own issues with Signal, the fact they don’t allow third party clients, you can’t self-host, they have a proprietary shim in their stack that only they know what it does, they were pushing crypto, etc, but at least Signal is better than this garbage.
It’s pretty drastically harder to register 100 phone numbers, especially in your target region, than 100 email addresses. Major spammers and such work with automation across many accounts, this isn’t designed around someone with 10 accounts.
They accept VOIP numbers, so… not really that much harder.