I'm an existing O2 pay-monthly customer, I have been for the last four years and I'm currently out of contract. I've got an 16GB iPhone 3G. For some reason, O2 thinks I am a new customer and supplied a new SIM. My online account currently has two account numbers and two mobile numbers allocated (my current mobile and the new iPhone one). In the O2 documentation with the iPhone it says if you're an existing O2 pay-monthly customer use your current SIM in the iPhone. If I do that what will happen to the new account on my online O2 account (which O2 have already started charging me for, so now I'm playing for two contracts). Is it best to use the new iPhone 3G SIM and transfer my number in iTunes or use my current SIM in the iPhone?