Hi.
I'm not sure if this helps, but!
Both T-Mobile and Orange use the high band of 1800MHz
And Vodafone and O2 use the GSM band of 900MHz.

Has your phone been in a situation where it has been in close contact with another phone where both have been left on?

The reason I enquire is that it may be possible that damage has been done when a phone sends it's ID to the network. My O2 does this every 20 minutes or so. If in a low signal area, the phone sends a high power signal, which could damage another phone in close proximity.

Just a thought.

Regards James Watt