Often these scammers use services that provide temporary numbers or even Telegram accounts, and after a period of time they sell them or the service provider sells them, and a third party may buy them. Therefore, this third party does not necessarily have to be a scammer, but it is better not to deal with any account on Telegram without using escrow.
Escrow has always been the most preached word to people to use ones they do business online most especially telegram. If the person doesn’t trust an escrow then you will see for yourself that he is scammer. Another thing again concerning Escrow is never use the one provided by the other party making the payment because most of them turn out to be scammers too working together.
As for OP I don’t see kidnap in this case because you can’t just kidnap someone and be using their phone it will be easy to track you down by that if law enforcement agencies who should definitely be looking for the kidnapper get involves