Contract cancelation

I've been trying to cancel my contract since I received it from the 28 of July till today m taken from pillar to post, one will say u need to do the cancelation in store , instore they will day you need to cancel it with the contact centre since it's an online application, the 7days cancelation period ends today and I don't wanna ruin my credit profile by reversing their debit order .

Secondly my bill for the past to months on my data plan it's a total mess with increment that I know nothing off and wen u call they always say you will be credit but dololo still