How to set up calls from the site?

Question

Telephony

Hello!
The task is set to receive calls in a self-written crm system. What is the best way to do this?
Options that I found:
1) voximplant.com/- it seems like Bitrix24 uses this platform
2) flashphoner.com - the price tag of $ 999 is somehow a lot for us.
3) Use Elastix. What are the JS libraries for calling?
What is your customization experience?
Where is the cheapest place to buy a sip number?
Web muzzle dialer with chat can you know where to get it?
Can you recommend something else?

Answer 1

I'm not sure that in all respects, but look at https://zadarma.com/ru/

Answer 2

Bitrix24, Megaplan and many others use VoxImplant, this is the best option