Ah right ok, I didn't read the original post and it makes more sense now that you have explained!
Sounds like you are having a pretty bad experience though. The call queues have gone through the roof due to the build up, and now release of the iPhone. Should start to die down soon..
Yeah there does seem to be a constant circle with some mail issues. If someone calls to confirm that the address of a customer is incorrect or mail is returned then O2 will try to contact the customer. After various attempts and they are unable to contact the customer, they will place a restrictions on the account forcing them to get in touch. The details must be kept upto date also for fraud and security reasons.
The problems seem to stem when they are chasing a customer for debt. After 6months of an unpaid balance, it is then passed onto a debt agency. The account is then closed and disconnected under the address at the time. The debt is then taken over by the agency who will continue to chase the person for the outstanding balance. Any contact between the person and O2 is then done through the debt agency.
I would personally advise to contact the debt agency directly, they can confirm you are the tenant of that address and have been for so many years. They should then liasion with O2 to confirm these details. The debt agency are directly responsible for that account now so best to speak to them