United rewards - debit without authority!

Got an sms offering a loan, rep**** to the sms, call centre contacted me and explained loan process. Took my bank details etc then at the last minute tells me I need to sign up for their full package before they negotiate a loan for me. At that point I told them I do not give them authority to debit my account and I am not interested in any product they have to offer. Their voice logging surely would have the full conversation. I told the consultant again I am not interested and do not authorise them to debit my account and I put the phone down. I then get an sms saying welcome to United rewards mall and subsequent sms messages from their partners . My account was debited. I disputed the debits and stopped them at my bank. For the last 4 months they continue to debit. I tried calling the call centre and explained to the consultant that I do not want them to debit my account to which she seemed understanding and said she would cancel it with immediate effect but still my accounted is being debited. I will be speaking to my bank to draught a letter and will be opening a case of ***** as I did not at any given time give authority to have my account debited.