I need to replace my uninsured, stolen Samsung D500. I am 2 months into a contract with BT Mobile, who will not let me reduce the tarriff and pay off the rest of the contract. I would like to buy an O2 D500, and put my BT Mobile SIM into it until such time as I can persuade them to let me cancel. Will this be possible, or will I find the O2 phone 'locked' and unable to take my BT Mobile SIM. Any advice appreciated!