Poor cellular connectivity at specific location? T-mobile says it my phone. It's not.

Where I live I have 5G UC and am fortunate to have blazing fast mobile connection using an iPhone 15 pro. [screenshot of 1336Mbps]

However, while I am at a town at the beach, I have 5G but no connectivity. Support has had me reboot my phone several times, even reset the network settings on the phone. No change. [screenshots of 4.14 & 7.96 Mbps] There are towers located relatively close to me. [screenshots of towers]

I have tried working with T-Mobile support on three different visits to this problem location. First I was told my phone is the problem. Next time they were "working on the towers". The last time I was told it was my phone. I'm very frustrated as I have no connection to do work with this poor connection. I have tried using the support techs and tried all the things they suggested, knowing it seems that it is NOT my phone. I will be at the poor connection location later this week and expect the same issues.

How can I get someone to look into the connection issues at the location and stop saying my phone is broken? Thank you for any advice!