loss of carrier signal requires a reboot

hardware is an iPhone 5 on Vodafone in the UK running ios 6·0·2 (10A551)

when the phone losses its carrier signal I have to reboot the thing to get the signal back, trying the trick of changing from automatic to manual doesn't work.

also notice as soon as I plug in the charger it losses signal also

this is very frustrating and I am getting slightly knarked by what I consider a flaw in the operating system