How to organize a broadcast over gsm?

Question

Broadcast

I have an interesting task before me. There are phone numbers, there are about 15 of them, of various operators. It is necessary to organize everything so that the audio conference, which takes place live, is broadcast to these phones.
Now everything is done very sadly. A column is taken and telephones are placed near it, on which they call the right people.
I thought I could use a gsm gateway for such purposes? To make everything more organized and profitable.

Answer 1

I heard about special services for this case. Issue some kind of conference number. Google.