How to make calls from Android without built-in GSM, via GSM?

Question

Android

Actually there is a Samsund s6 edge live demo unit. Which differs from the usual lack of gsm, lte (they are not soldered on the board, and it is impossible to solder)
But I want to call him. It is with him that I want to emphasize it.
Options that I could find:
1. SIP. Connect Sip with a real address and set up forwarding from the main number.
+ carry an additional gadget for distributing the Internet. Cons: the second gadget + double payment for communication + interruptions in communication, where the Internet does not catch.
2. Gmate, a special device with a built-in gsm module and bluetooth transmission. Cons: the second gadget + poor connection + not all versions have 3g, and not one lte + can simply not work with a specific device + cannot be found in my city.
3. 3G modem with the ability to make calls connected via usb-otg. Pros: can be succinctly cut into the bumper body. Cons: Vague implementation (little information and only with a tambourine) + busy charging socket + power consumption
4. On s6, try to simulate a bluetooth headset (to connect it to another handset as a headset) Cons: Vague implementation + the chip may simply not support
Actually questions:
Has anyone tried to implement something similar? How is it going?
Any other implementation ideas?

Answer 1

By the way, the problem is interesting and relevant.
For example, I have an Nvidia Shield Tablet, which can send SMS, but there are no calls (I always thought that sms also goes through the gsm module), while there is 3G-LTE Internet.