What is the best way to organize telephony in an online store?

Question

Telephony

There is an online store, which has already developed a little. At the moment, an old Samsung phone with 2 SIM cards is used to receive calls / orders. At the moment, this method already leads to many disadvantages, since it is not possible to fully record conversations, and also in the future to distribute calls to 2 operators. Actually, the question is, what are the simple solutions for organizing telephony in IM?
I read somewhere that you can buy special gsm modems, but I did not find any useful material anywhere that would explain what software you need to use for this and how to set everything up.
I would like to eventually find some solution that could solve:
1) Recording conversations
2) Setting up an answering machine that would work if no one is available
3) Receiving SMS
4) Sending SMS (optional)
5) Distribution of calls between operators (optional)
6) Ability to work with Ubuntu software (optional)
Initially, the idea was to organize everything on a small crutch. Take an Andorid smartphone and connect to a PC via AirDroid. But there may actually be a better solution.

Answer 1

Raise your server with Asterisk, connect 3g modems with sim cards to it. Firstly, it's free, if you figure it out yourself, and secondly, all 6 of your points will be implemented.

Answer 2

Connect a virtual PBX with forwarding to any mobile number.
A selection of links

Answer 3

Google "virtual PBX". You can find many solutions: from budget to cool corporate pieces.
In your case, zadarma or binotel will most likely be suitable. I use the latter in my online store, but I am very dissatisfied with the quality of communication.