U verse new modem 5268ac constant Disconnects

Att u verse 5268AC

We have been having internet issues EVEN ETHERNET connected. It isn't the computer as this goes for all devices.. 

It can't seem to last 5 mins without it disconnecting 

Not good for gaming or streaming 

Run diagnostics on windows 7 and it just says

The DNS server is not responding..

This wasn't happening before. We only had TV issues so they switched it..