I have lost my O2 sim card overseas and on realized that when I came back to UK after four weeks. I reported that immediately, but I have been told that someone found it and used it. Now I have a £3000 bill for duration of four weeks that O2 company has cleared £2000 of that from my account and there is still £1000 remaining to pay. The phone company says that it is all my responsibility. While I agree that I am responsible for the sim card I cannot believe that O2 had no limit for calls and have no strategy for protecting their costumer and that I never asked my phone to be activated outside UK. I desperately need legal advice to see if I have to pay all of this huge bill and if O2 is responsible in any way for not realizing that there is something wrong when a £26 a month bill goes to £3000 suddenly. Please advice.