I would like to change my mobile phone on my online account. I have a new phone that uses the same size SIM. I've already installed the SIM in the new phone and the new phone works fine. I just want to change the phone on my account but none of the options apply to me. In "upgrade my current phone" it wants a new sim number and the other option is that my phone doesn't require a SIM. If I enter the old SIM number when prompted for a new SIM it says that it is already in use.