No calls when wifi is on

I can't get any calls when I select wifi!!! I even have an xfinity router so I am furious right now! My husband has accused me of cheating because when I'm at work or home it goes straight to voicemail! I have been dealing with this for a year now have a new galaxy and all updates installed. I think I'm going to T Mobile. Xfinity owes me money for all the calls I didn't receive!