iPhone problems with O2

[Keytapper]

Have been over a week now discussing problems with the above via Twitter and o2 chat line. Firstly, do you know if o2 disconnect phones that have not been used very often for making calls on their 'Pay as you Go" tarif?
The last couple of weeks, my phone will not connect to the server for making phone calls. Wifi and e-mails all ok. The guru in our local o2 store has made alteration several times and all works well until I get home, and although computer and shop tell me the signal is all right in my area, I cannot connect. Yesterday the guru altered it to connect with G2, which is in my area and all worked well for the rest of the day until I got home last evening ans then "No service". Same today. Any ideas? The phone is about 7 years old!!

[Calum]

Firstly, yes it's normal for numbers to be disconnected if they're inactive for a while, policies vary from 6 to 24 months and I'm not sure what O2's is off the top of my head although I'm sure they could advise.
Does the phone work with another SIM?  Either the same network, or another if the phone is unlocked?
Have O2 tried a SIM swap, keeping the same number but using a different SIM?  That would've been one of my first steps if I were them - I'm not speaking as a phone company technician but someone who has managed a fairly large Vodafone contract so I did a lot of this sort of troubleshooting including SIM swaps and reprovisioning.

[Keytapper]

Thank you "Egghead" for your reply. I have tried other Sim Cards but the result is just the same. Yesterday, a text message got through from O2 asking what I thought of their Guru. After quite a time, I prepared a reply. Of course I could not send it as the connection was down. This morning when I turned the phone on, the connection was made. I quickly tried to send yesterdays message that I had prepared, but the connection dropped before the whole message was sent. Knowing the trouble I have, why can't they connect with me via e-mail?  The wife thinks its due for the bin. Resale value to O2 now 20p!!

[Calum]

If you've tried other SIM cards, I can only assume the issue lies with the phone.  Not being an iPhone expert and having in fact only ever touched one once or twice, I don't really have much to offer in terms of troubleshooting steps.
I gather from your original post that the phone used to work OK, did anything change between it working and not working?  Any sofwtare updates, for example?

[Keytapper]

A shot in the dark....we have had a Smart Electricity meter fitted with a hand held monitor. The monitor packed up after a couple of weeks. Stray signals??
Thanks for your replies,  Pete.

[Calum]

I suppose it's possible but not sure how easy it'd be to confirm that.