AT&T Fixed Wireless Internet Connection Issues

I just had the internet installed this morning.

It seemed to be working fine, and then the connection suddenly dropped. No internet access. It randomly connects again, then disconnects again. We're not installation techs at this house, but we know our way around a router/computer/IP settings (you get the idea). I was streaming a video in 720p earlier without any issues, and I am now having MAJOR issues watching in 160p, 360p, and 480p.

Has anyone with the fixed wireless internet had the same issue? If so, how did you resolve it?

Thanks.