It doesn't seem to matter what mobile you have, Samsung A series or S series ect, if the network you are on is rubbish e.g EE, O2 or Vodafone etc then the phone won't work to it full potential. We need to get these companies to improve infrastructure.
I've been with EE for a number of years and really like them but the only problem is sometimes they do suffer indoors due to their lack of lowband spectrum. I use a Vodafone SIM as a 2nd SIM as Vodafone have a good amount of lowband spectrum
Vodafone would never go my wife was with them before EE the customer service was terrible and trying to sort out her bill when they overcharged her horrible never ever again
Should have built one network with all operators using that instead of 5. Its how the most of us get our home broadband, and don't need a new phone line everytime we change provider.