found an unauthorised debit on my account

Good Day<br> <br> I checked my bank statement on Friday.i found a debit order that i don't know off.i wen't to the bank on Saturday they gave me this numbers to call 0126655750.i called them this morning i found this lady who gave me this numbers to call 0318118953.i called this numbers and spoke to Michele.she told me that it's a promotion company she is going to check what happened she will call me back after an hour.she didn't call me back.i called them again and spoke to some guy who said that Michelle went to a meeting but he knows about my story.that it was a mistake they are sorry they will reverse the money and cancelled the contract.Am not happy about their respond.I want know were did they get my banking details from.And who gave them the right to go into my account and take my money without my concern.I didn't't join the policy , i don't know anything about this people.please help me out , because they have my banking details am afraid that they might go into my account and take money.<br> <br> Kind Regards<br> Sarah