iPhone 15 Pro - ongoing poor cellular reception and lack of responsiveness even with 5G+ and 4 bars

I've asked about this before, but never received any responses. Both Apple and Bell Canada say there is nothing wrong with my phone, yet this is the worst performing iPhone I have ever owned. I frequently cannot use apps or get responses from browsers when searching, even if I have 4 bars showing a solid 5G+ connection. Any suggestions regarding why this phone is so terrible and cellular reception is so bad? On a side note, when I went to Indonesia in the summer, and used an eSIM, cellular reception was much better.