4G coverage (and calls dropped)

[AXC33]

Since 3G and 4G have arrived in my area (sort of), I find that calls often drop as, whilst masts about 4 miles away were upgraded to 3/4G, the ones local to my town were not - they're only 2G (despite planning permission for 2 O2/Vodafone upgrades being granted a couple of years ago). The rollout seems to have stalled! Therefore indoor coverage is pretty bad for data and it doesn't always switch from a distant 3G mast to a closer 2G one - calls get cut off instead. I know I can switch the phone to 2G only, but not ideal. Contract ends soon & might be an opportunity to research the other networks perhaps?

[MI5]

Just get PAYG sims from other networks and try them out. All networks will send you free sims off their websites.
If you need to unlock your phone, follow this help guide https://community.o2.co.uk/t5/How-to-Guides/Unlocking-an-O2-phone-to-use-a-different-SIM-card/ba-p/1...