Incorrect billing

I purchased a mobile 5 days ago, and I totally regret it. All because of the appalling service I am already getting from the service provider. The payment agreement is the 1st. However 2 days later my account was debited without my knowledge nor consent, and without explanation. If you guys are going continue debit my account as & when you please. I'd rather make manual payments. Please explain that cost & compensate me for the bank charges which occurred as a result of your doing.