iPhone 12 Pro Max - Signal issues

I’m in the UK and recently upgraded from an “Xr” on O2 to a “12 Pro Max” on Sky. Since doing so, my calls seem to just drop and signal strength both indoors and outdoors is not great at all.

As I had upgraded phones and changed networks, I wasn’t sure what may be causing this severe disruption. As the “12 Pro Max” is not really a new handset, I put the issue down to Sky. However, I also know Sky use the same masts as O2 so a part of me knocked that on the head.

I got in contact with Sky who ran me through various settings and in the end, sent through a new SIM card. However, the issues were still occurring so today, have told Sky I will be cancelling my contract with them in addition to returning the handset.

I got back in contact with O2 who will be sending me a new SIM and therefore putting me on a a SIM only deal, which I’ll use with my old “Xr”.

From reading various posts, it does appear I’m not alone in experiencing the dropped calls and loss of signal issues with the 12 Pro Max?