I absolutely second @jremington 's post!!!!
Don't mess around with mains voltage.
Phones are not designed for this kind of voltage and current.
P.S. Have a look here https://en.m.wikipedia.org/wiki/Telephone_line#:~:text=The%20voltage%20at%20a%20subscriber's,and%20ring%20at%20%E2%80%9348%20V.
And be aware that you may safely use higher voltages if the current is limited which you don't have with mains.