How to independently organize telephony for calls from the site?

Question

Asterisk

Good afternoon everyone.
There is one site - a large catalog of enterprises, traffic ~ 150k visitors per day.
The company card has contact numbers - mobile / landline (city).
I would like to organize the opportunity for visitors to call for free to any number of any company that is represented in our catalog through its browser.
I don't know much about telephony.
Which way to look?
Is it possible to organize this on your own, using, for example, 30 SIM cards, and some kind of gsm-mini-ATS? What will be required for this?
Or, in this case, it is more expedient to contact a company organizing such services? What company can you recommend?
Which of the possible options will be minimal in terms of the cost of service (I mean both money and man-hours)?
Thank you.

Answer 1

Asterisk + webrtc + any telephony provider (GSM, IP, E1, analog).