Telegram is not a good platform to conduct your transactions through. Scammers often deal with it, so if you want to make any transactions, you can deal through the Escrow Service or other websites that act as a mediator between you and the seller. If the seller requests that you send your money first, you must refuse that because if he does not have a great rank other than a newbie rank and a good reputation in the forum, he will 99% steal your money. He can create a new membership on Bitcointalk and change his username on Telegram as if nothing happened, so you have to be careful; once again, please put chat logs and proof enough to support your topic.