We already have developed telegram bot and can show you demo first. You need the bot where you can extract userids from other telegram groups. Then they should be added to your selected channel. Please confirm I understood you properly. We can show you demo first and then you can award us the job.
Hi, I have a working program (runs on windows, mac and linux as well) and I can explain the method itself
If you have additional questions please contact me.
Best regards, Krisztian Adam