I have an old Western Electric model 500 telephone, and recently picked up an amazing device called a XLink BT2 https://www.myxlink.com/bt2.aspx
It allows you to connect any old analog POTS line to your cell phone. Even old Rotary phones.
It works like a bluetooth headset you would use in a car.
I soldered on a modern end to the phone and had it setup quickly. Now if you ever call the lab, I will probably answer on this phone!