How to combine receiving incoming calls on a SIM card and voip telephony for outgoing calls?

Question

Telephony

What we have:
- A SIM card with a beautiful number for incoming calls from customers;
- Mobile phone where this SIM card is actually inserted;
- SIPNET account for making outgoing calls within the country and beyond;
- WEB-interface SIPNET through which outgoing calls are made.
What we want:
- One handset that will receive calls from a beautiful SIM card number, and make outgoing calls from it using a SIP account.

Answer 1

If a mobile phone runs on Android, then it has a built-in SIP client, for the most part from version 4 of the OS. Set up and call.
For example, so

Answer 2

The solution to your question is quite simple.
Setting up incoming and outgoing communications with telecom operators.
From known to me it is www.votbox.ru/?partid=2915
My colleagues work with this service provider.