How to organize calls from a phone through another phone?

Question

Telephony

How to organize calls from one phone through another, connecting to it via Wi-Fi? For example, I have a plan for unlimited calls, but I want to share it with my mom. How can I make her call like from my phone, but through Wi-Fi?
UPD. About a variant with connection of two subscribers I know. I would like an option without my participation for each call.

Answer 1

Put the SIM card in the modem, put the modem in any piece of iron that will pull the asterisk.
The second option would be to push the asterisk directly to the smartphone, but it can be difficult to get it to call somewhere there.

Answer 2

what is this all for?
"all inclusive" from the beeline and do not worry your brain) pay for your family on one balance.
ps True, they did not do well (relative to me) with a change in the conditions inside the tariff in the tariff "all for 900"!