This post really resonated with me and I felt the EXACT same. I wanted to walk in the AT&T store (where I purchased) & throw it back at them instead of out the window. I had tried everything. Hard reset, wiped it clean, re-uploaded from cloud etc nothing worked. On Wi-Fi it worked ok but off it the phone was literally not functional. Was having to call & get directions bc couldn’t even use my map or Waze app.
At AT&T store they kept telling me it was my data plan & I finally agreed to upgrade to premium elite data or some crap. It seemed to fix the problem & from what I understand if you don’t have a newer data plan that can work with the 5g technology then it’s like “putting a Honda motor in a Rolls Royce.”
This all happened today so I’m intentionally working off Wi-Fi & will give it a couple days. If it doesn’t fix the problem I’m going back & getting another iPhone 10 or something. Screw the 13! I’ve had iPhones since they first started selling them ~ 2006 ish & I’ve never had an experience as awful as this!
Update your data plan if you can. It was only about $10 more /month for me. Fingers crossed it’s REALLY fixed!