I'm not sure if a Telegram user can be reported, but if there is such an option I would definitely use it - at least to try to make his life a little bitter.
Yep, you can report Telegram scammers. As far as I know, there are few ways to report them:
1. Simply contact @notoscam on Telegram and give all relevant info on scammer you have. As usual, the more you provide, the better.
2. Contact
Telegram support and explain the issue, again giving as much info as you have
3.Then again, you can also report user for spamming, and again if enough people report the same account, he won't be able to send PM for certain period of time.
If report is valid scammer will get "Scam" tag on their account, so everyone knows whats going on. Unfortunately, I think that people rarely bother to do that as those scam tags are rare, I've seen maybe 10-15 of those so far and I am heavy Telegram user.