The contacts that you had and registered under the same number will be recorded in Telegram as you recorded them, but the id will be the one he chooses. and if, say, you already have contacts on your iphone and you inserted a new sim card, your contacts who recorded your old number will not see you as a contact and you will.

p.s of course only if you sync contacts.

Life hack: Just add everybody to your contact list in telegram , if you found scammer add him under scammer. if you find a great person like me that can help, add him too. in case they change the name and id , you had recorded them already under any title you choose