I am curious now can you explain more? As far as I know Telegram requires a unique phone number for every account on registration.

It does require a phone number to make an account, which makes actually creating multiple accounts a huge pain, but bizarrely enough once you have the account set up you can log into as many of them as you like in their mobile app (I don't think any of their 3(!) web apps support it though, but that's not hard to work around with containers). In comparison discord makes setting up multiple accounts easy but the app has no concept of this so it's a pain to manage (I don't know of a good way to have two instances of it logged into different accounts).

Yes, you register your work account with your work number and your personal account with your private one.

Telegram clients support multiple active sessions with multiple accounts, you can switch between them easily and receive notifications from all accounts.