Does COMCAST have poor quality phone service?

Does COMCAST have poor quality phone service?

I switched yesterday from Verizon FIOS to COMCAST and had terrible telephone calls today on the land line.

I think we were sold >100 GPS upload speed. So, I doubt the poor quality is due to a slow internet connection. But maybe the old Verizon FIOS phone number was what they called a POTS line, a Plain Old Telephone Service line. Those were the ones where you cold hear pin drop.

Did I move from a POTS Line to an Internet based phone? And is that the cause of the major drop in quality?

My new modem is...

Xfinity
Dual Band Wifi
802.11.ac

The phone cable goes into the back.

Would an Internet phone do better?

Is there anything I can do?

I really despise having poor phone quality and may go back to Verizon to escape a bad connection.

Suggestions?

Thanks