Good signal/bars but no network connection many times daily

I am having the same issue in SD.  All members of my family have an iPhone 12 and all of us show 4 bars on the 5G network but we constantly are loosing connections with Apple Music, Maps, Podcasts, texting, to name just a few.  I have been sent new SIM cards from T-Mobile that were suppose to fix the issue and it did nothing.  I have tried switching to LTE but we have the same issue with LTE.  I am not even getting 1.0 Mbps upload speeds.  I wanted to love T-Mobile because the monthly charges were so much lower but I am going to be forced to switch back to Verizon because our phones are not even usable with T-Mobile.  Unfortunately,  all phones are locked until we pay out our obligation, which makes no sense since two of the phones were suppose to be free.   If T-Mobile cannot fulfil their obligation to provide service why am I obligated to payout my contract?  Frustrate in SD where the map shows 5G Ultra in the urban area I live in, but extremely slow speeds.