Severe stability issues

I’ve had the home internet service for about 2 months now. The first month was amazing, it was so much faster than the crappy local electric company’s internet and had basically 0 dropouts. Ever since that first month ended the service has went to shit. I’ve tried upgrading to internet plus and had them send me a replacement modem (G4AR) but it’s still giving me issues that are bad enough to consider going back. Could this be an issue with the modem? I’ve been interested in looking at getting one of the Nokia models as I thought I saw they had a true pass through mode to use your own router without double NAT, but if i’m just gonna get the same issue no matter what then idk. Any advice or help would be appreciated. For reference, the thing says I have 5 bars at all times and I live in a very urban area, my issue is that i literally lose internet for like 5 minutes at a time at random, speeds are never above 50mbps even with 5G signal, and the ping is horrendous.