I'm guessing that this was the transaction that you paid the "admin" with:
https://www.blockchain.com/en/btc/tx/7b93279b5a78c9fe5b4db64c5da9baa26d049c0a1ade39d047eabbb97da6ed9e? Why did you wait 2 months before coming out and creating a scam accusation? You should have done this way earlier.
A possibility as suggested by Joel_Jantsen is that the person you contacted is an impersonator of the actual channel. It would be extremely illogical for even a scammer to not post your content on a telegram channel, since that is completely free on their end anyways.
If you can be sure that the person you contacted was the admin, then where did you find out about this person? Does this person have a bitcointalk account? If not, then there is really nothing you can do. He's taken your money, and there is pretty much no info of him anywhere. Don't ever deal with random people without escrow.
The whole telegram group seems to have an artificial amount of followers. It's probably got very little organic members.