I got my Sensation unlocked from t-mobile (UK) so that I would be able to use another SIM in it. The other SIM is low priority, one I would just need for a couple of months to call one person on a preferential rate, 99% of the time I want my t-mobile SIM in the phone. Unlocked it via an unlock provider who sent me a code, input the code, all went perfectly. I booted up on O2 and it started receiving my messages. There was something which came on the screen briefly about selecting networks but I mishandled the phone at that point and accidentally touched the Home button and it wiped the information off the screen and it refused to come back, so I don't know what that was about and how essential it was. But now when I put my original t-mobile SIM back in the phone it comes up "No SIM card". The card works in another phone and the other t-mobile SIMs I have also do not work in the newly unlocked Sensation, it now ONLY works with the other networks!! I'm waiting on help from the seller of the unlock code, but not holding my breath. It's an un-rooted phone and it's been mine since new so it's totally factory except for normal app installation and updates from HTC. I am not mad about the idea of factory resetting it but is that likely to help? I have read it does not take away the unlock anyway, but maybe it will go back to being able to read t-mobile SIMs. Anyone had this problem before? Anyone know what to do? It could be tomorrow before I hear anything, meanwhile no phone, which is a disaster for me.