Why not run a campaign here where you can possibly get a organic members on your telegram channel, since adding members without their personal consent will result to a mass reporting to your channel as well you might get a fake member which will not contribute on discussion also in development of your project.

Hire a reputable campaign manager and he will discuss the things you needed and also don't forget to have a promotions/competition so that your real users will have reason to stay and will not leave.