Implementation of soft mini-ATS. GSM number?

Question

mobile connection

Good afternoon!
I'll try to more or less clearly describe what I have and what I need:
- There is a GSM number (with a "binding" to the city, a regular SIM card) from a mobile operator.
It is necessary that:
a) when calling this number, customers hear the invitation of the auto attendant:
“Hello, you called the Horns and Hooves company, to connect with the sales department, press “1”, etc.”.
b) Further, according to the results, a call from this number should be forwarded to the mobile numbers of employees or to a wired landline number, which is physically located in the same place where the soft PBX will be.
c) There must be full logging of calls and actions.
d) Favorable long-distance calls. I see it like this: An employee dials a mobile number, on which a mini-ast and then a mini-ast dials the required number via sip. The cost of a call for an employee is a sip-tariff + a call to a mobile phone.
e) Voice mail. It is critical that not a single call is lost. For example, if all employees are busy, their phones are unavailable, or there is simply no answer after 4 rings - the call goes to voice mail - an answering machine.
Actually questions:
1) What iron is necessary?
2) What software is preferable to use? I would be grateful for more or less detailed manuals, because I have not yet encountered soft mini-ATS.
3) Required server configuration?

Answer 1

On the software side, this can be implemented using Multifon from Megafon and Asterisk www.multifon.ru/publications/settings_ip_pbx/

Answer 2

You can really enjoy building your own PBX from a USB GSM modem (Huawei E1550 works well) connected to a netbook under Linux and Asterisk with the chan_datacard module . Everything else practically comes down to setting up the software and the dialplan.
And you need two modems :)

Answer 3

You can do it easier, all the functionality is in VATS