Why is it that sometimes I can be in the same place (at home in Gloucestershire) and one day the signal for my mobile will be fine, and on other days there will be no signal for many hours? I'm on the Orange network.
It could be that the transmitter that you are registered to is down. There are two of us here both on Orange and a short time ago my phone worked but my son's didn't. I telephoned to report his phone and it was explained to me that even though we are in the same house we could be on different transmitters. It depended which one you were put on when you registered the phone.
also weather conditions, if it is a great day it will be easier. this is quite relevant for umts as I have a touch and go transmitter and sometimes get kicked off onto gsm