How to establish communication from a blocked network?

Question

Telephony

Hello.
There is such a situation that in our most popular of all republics (dnrii) it is very likely that Ukrainian mobile operators will be turned off. The "authorities" of the DPR demand "to obtain a license to carry out activities in the field of telecommunications." With a probability of 99.9%, none of the big three (Vodafone, lifecell, Kyivstar) will go for this, which means that only one local operator will remain - Phoenix. From Phoenix, you can call Ukrainian and Russian numbers, and the called subscriber will display a city Donetsk number (as I understand it, all this is organized through a gateway), but you cannot call Phoenix itself.
Unfortunately, I am not very familiar with IP-telephony and therefore I ask for advice on how best to establish communication between Ukrainian subscribers and the DPR. You can, of course, through instant messengers, but the peculiarities of the company's work (wholesale and retail trade) do not allow using only them. It is necessary that both customers and managers can call from mobile to mobile.
ps Phoenix already has a poor 2G Internet, soon they promise to cut down 4G, but something is hard to believe.
Thanks in advance.

Answer 1

Any SIP operator. There are really a lot of them.
Roughly speaking, you will have a certain number - even Kyiv, even Cypriot, they will call him, and calls will come to you.
In general, this way you can even raise communication throughout the city - traffic through the Internet.
As options - well, put a GSM repeater. A better and higher antenna - maybe it will break through. But this is only if you cannot live without mobile phones.