How to deal with calls from non-existent phones?

Question

Telephony

There is a work phone, a cell phone. At the most active time of client activity, an attack occurs from different numbers, there is a constant dial-up, when you reset, the dial-up is automatically repeated. We tried all the numbers from which dialing occurs, add to the black list, new numbers appeared, reached the limit of the black list (it turns out there is one!) Due to redirection, we increased the capacity of the black list, but new and new non-existent numbers continue to attack.
Tried to call back to the number, in response they say "the number does not exist."

1. How to get information about the source of the attack without the help of special services (no sense)?
2. And what methods to deal with a loaded phone so that customers can get through?

Answer 1

1. Contact your carrier.
He has the ability to track where such calls come from.
If from another operator, then they will transfer an appeal to it and so along the chain they will get to the source of the problem.
2. Do not use SIM cards as such to receive calls. Usually they redirect to SIP numbers or place SIP numbers in advertisements right away.
This gives you almost unlimited multichannel and unlimited whitelists and blacklists.

Answer 2

1) these are calls from sip telephony - Internet telephony, if you wish, you can also set up calls with number substitution.
2) many ways to get rid of such attacks. You are still lucky, there are services that attack numbers in a complex, for example https://blocksim.ru , they can also remotely block a SIM card there. In the same place, consultations are given on how to deal with such attacks.