T-Mobile Manual Network Selection

I bought the iPhone 14 Pro unlocked from apple.com and added a T-Mobile eSim to it and that's it. I leave my network selection on automatic just because it is like that by default. I was on a road trip and I had no service with T-Mobile so I put my phone on airplane mode for around a minute and turned it back off again. when it re-connected instead of being on T-Mobile it connected to AT&T. I was very confused because I don't have an AT&T account let alone an eSim. I had like 3 bars of AT&T LTE but it was so slow. I tried to re-open my maps app and it would not load at all. I just saw the blue location marker and the grey grid. Once I had no service on AT&T it waited for a second before changing back to T-Mobile which had a service and never changed back to AT&T ever since even when I have no service and the setting is left on automatic. I also recently tried to do this again, going manual and going from T-Mobile to AT&T and it is not working with no service. And Verizon also pops up and it doesn't work either. If anyone knows why this happened please tell me because I can't find answers anywhere. Thanks!