Why does my iPhone 16 Pro Max keep failing to activate iMessage, and how can I fix it?

My iphone 16 pro max is literally the worst phone I have ever had......been using Iphone since to Iphone 4 and I am considering an android now......

My phone constantly stops working, stops making calls, stops being able to text, stops being able to open the settings app, stops accessing anything internet related while connected to fully functional wifi.

In the most recent adventure it shut off Imessaging and won't turn it back on. Keeps saying "activation failed". I can still imessage on my ipad and/or laptop sitting next to the phone on the same network.

Does anyone have an explanation as to why this phone has been so glitchy and completely unusable for close to 40% of the time I have owned it?

I got it new from T-Mobile about 5 months ago. It has been in a case and well cared for since I took ownership.

[Re-Titled by Moderator]

Original Title: Imessaging stopped working