No dial tone, again

This is at least the third time in a week that we have lost dial tone on our Xfinity voice line.

We run a business out of our home and need the phone line to work. This is unacceptable.

A technician visited last weekend and left the line working, yet today we discovered there is no dial tone again.

We have a separate modem for Xfinity voice, and the data Gateway for Wi-Fi and cable is functioning perfectly. Why does this issue keep happening? How can we get a permanent fix so this does not continue?