What do i do about a lost contract sim card?

I'm on 02 monthly contract and i have misplaced my sim for my iphone 5. Does any1 know if i can get this replaced?

All you need to do is go into your O2 shop and ask them to disable your lost SIM card and they will give you a new one with all your contacts etc transferred onto it. They have it all on computer, I done exactly the same with my iPhone5 sim! Simple.

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