We have a dial tone, but the other line can’t hear me at certain times a day

For the past week, the only time my phone fully works is from 2p-8p. The rest of the day, I HAVE a dial tone but no one can hear me. I can hear the other person perfectly, but they can’t hear anything I say. Just silence. 

During that time, my message system voice is all garbled and I can’t hear my voicemails. 

I have a Panasonic KX-TGF380, I’ve tried calls using the base phone, as well as the other 2 cordless phones but nothing. 

Cox has sent out 3 servicemen but they have zero clue. They have completely switched and given us new lines and new modems and everything. 

Any ideas or help? Happening to anyone else?