Why does an iPhone 15 plus drop to 3G signal?

[Ndl2]

My iPhone 15 plus can get patchy 5g signal outside but drops to 3G indoors which is problem with digital switch off soon of 3G in my area. 

why doesn't it drop to 4g? If I tick 4g in settings it drops to E (2g).

sky mobile have no idea when I call and I've reset network settings etc. 

I also don't like the fact iPhone 15 doesn't have a VoLTE toggle because you just have to assume it's switched on.

really concerned. Thought I should get a new iPhone but tbh might just be the same. Any ideas?

[63johnw]

Hi @Ndl2  you could take it to an Apple Store and get them to run a diagnostic check to see if they can find a fault on the phone. Have you tried a new sim ?