my iPhone 5s reports signal strength of between no signal and 3 out of 5, varies by time of day. If I turn off my Virgin modem to stop WiFI I get GPRS not even 3G never mind 4G but the maps using geography and theory report good signals. What is going on, do you ever send detector vans to check the theory, when will my contract expire so I can unlock my phone and move to Vodaphone who have a good signal here? I still keep my Voda PAYG for emergencies. Post code GL51 and you can presumably get closer than that from my IP address.
Usual response, Virgin only look at theoretical maps and never check actual signal strength. It is a pain to have to drive to my local supermarket to get a usable signal. The actual signal is so variable it must be a load problem but they never admit it. Last no signal for a few minutes at about 15:30.