Frequent Disconnects on Fixed Wireless Internet

For the last two weeks or so, I've been having frequent disconnections with my Fixed Wireless internet. (On the modem, the lights remain green, except the Service light turns off. And I have no internet access on my devices.)

This is often resolved by hitting the Reboot button on the modem, but sometimes that does not resolve the issue immediately, and 10 or 20 minutes pass before internet is restored.

For the last two weeks or so this has happened at least once a day. These long unexpected periods of lack of internet is harmful to my business, as I work online, and have already lost a day of work (and thus pay) to this problem!

Yesterday I spoke with tech support over the phone. They had me unplug all devices, for ten seconds, plug them in, and performed some sort of action from their end. They spoke of "network congestion" and said that the problem should now be fixed.

However, my internet again went down late last night, and again this afternoon.

The problem has evidently not been fixed.

I suspect that the modem might be bad, and need to be replaced? Are there any other possibilities? If the modem does need to be replaced where do I go to have one sent to me?

Thank you for your help.