New iPhone 13pro poor network coverage

[LiGrice]

Hi just swapped  from iPhone 11 to an iPhone 13pro with a new sim and since doing so my network coverage has been terrible. 1 bar 5g most of the time doesn’t swap to 4g the phone is really lagging behind, call quality is terrible and sketchy face time buffers. The phone also struggles to connect to my home Wi-Fi 99%of the time when my iPhone 11 never had any issues! What’s Going on … feel like I wish I’d saved myself the money and kept my old phone 

[MI5 · Accepted solution]

@LiGrice 

You can contact Apple to get a diagnostic check run on the phone https://www.apple.com/uk/retail/geniusbar/

Or return it to O2 as faulty for a replacement https://www.o2.co.uk/help/device-and-sim-support/returning-your-device