Facebook advert help

Hi this morning I put an advert on to last one day for £1 this was my first time for advertising.. so just had another look at the promotion page and I've by accident pressed something that is going to charge me £85 for a day but this is something I don't want as I was only trailing the advert hence why I did a £1. I have tried to find a way of contacting Facebook as it needs to be Canceled can anyway offer me any help pls? Much apreciated. Thanks
 
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