Ringer turned off do not know how to turn on.

I'm not sure if it was the solution or just coinsidental that I replaced the handsets in the base, and unplugged power source and phone lines for
just a minute and then plugged them back in and the ringers came back on. I don't know for sure but we have had a frequent problem losing dial tone with these phones and it is the same thing we do to correct that problem.
We have Charter cable bundle package for phone service .