I have recently recieved an old phone (not old but my friend does not use this anymore since he got a new phone) from my friend who was using tesco mobile. I have just inserted a new sim and it will not register my giffgaff sim inside the phone. I have searched through the list of HTC phones that are on the giffgaff website's unlock guide list and cannot find the htc desire 610 on any of the 9 pages or drop down list. i do not trust most sources on google that it comes up with. If someone could give me a trusted source or guide me through the process i would be very grateful.