I'm on a sim-only deal and have recently bought a new phone (Sony XA2), and transferred the existing SIM into it. I have the mobile data set to "3G (preferred)/2G" (I don't have a 4G SIM), and around where I live (north London) I'm now usually only getting 2G, whereas in my old phone the local signal strength was always good enough for 3G.
Also, I was in Canterbury yesterday, and had trouble getting any data to work at all, both indoors and outdoors, in various parts of the city (the Virgin website classes this as 'Good Signal Strength' for 3G).
Before I complain to the manufacturer, is there anything I can try on the network side to improve things?
I am sorry to hear you've been experiencing issues with the signal. You've advised you don't have a 4G SIM at the moment, am I right in assuming that you don't currently have a tariff that includes 4G data? Have you been able to try your SIM in another phone to see if you still experience signal issues? Were you able to check the reception levels you were receiving on the phone whilst you were in Canterbury? One thing we always recommend if you are experiencing connectivity issues in an area you should be getting strong coverage in is to run a manual network search to reconnect to our network, this will force the phone to connect to the strongest signal for that network which would usually mean connecting to a closer mast.
One other issue that may be affecting the connection is there may be a fault with one of the masts in your area that occurred coincidentally around the time you changed phones. If you're happy to provide your postcode I can take a look at the masts and coverage in your local area.