Mobile Phone Bill �7500 can they make me pay ? There not my calls!

[tuks19]

I lost my phone in spain last month and thought i had reported it to my phone company (o2) in the uk. i got my bill through this month and its �7500 of calls i havent made. what can i do? they insist i have to pay as i didnt report it lost - they have no record of me reporting it, calling them etc. and i cant prove i did as it was from a pay phone in spain.
my phone bill hasnt been above �60 for over a year and the highest its ever been is �300 about 4 years ago.
i asked them why they hadnt put a block on it and they say they have but only a week or so ago... surly they should of done this when it reached a few hundred pounds?
im at a complete lost end, i dont know what to do, i cant afford this! can anyone help... a friend has said to just tell them i wont pay it, but ill pay the remainder of the contract and the cost of calls upto the time i reported it lost, is this the best plan?

any advice at all would be greatly apriciated

[spammylou]

If they said they put a block on it but only a week ago then surely that proves you had rang them? If they say no why was the block placed on it?

You can ask for a transcript of any notes on your account i.e phone conversations etc etc etc. This is an exceptional amount and I would do any more correspondence with them in writing.