Unauthorised debiting by Ignition Group

Ignition group as been debiting my account for the pass 2 years , don't remember ever speaking to them now that i have stopped the debit , it has a negative impact on my credit score , tried contacting them on several occasions but to no avail , really shocked that i am being debited and my credit score as been decreasing for something that i didn't even agree to , They better sort this matter out , or else i will take this further .