Price Lock issue

I have recently spoken to a call centre agent to address an issue with my existing pvr decoder and this agent told me about the new Price Lock deal. I sent an sms to the number provided and received a call back. The agent explained that he must issue a new contract and needs my bank details. Something sounded 'off' about this as I have been a Multichoice customer for a long time and I am not comfortable providing bank details to some stranger calling me. MC have my details as I am already paying by debit order. I called the call centre myself and this agent explained that this the only way and promised me another call back from an 087.. number (for security reasons). I did get a call but not from an 087 number so naturally I refused to proceed. I then submitted a written complaint to MC and they explained to me that I needed to go through the process if I wanted the Price Lock deal. Again she promised to ensure I get a call back from an 087 number. This was on the 17th February and I still have not been contacted. I have a problem wt strangers wanting my bank details telephonically and would like MC to help me get the deal without compromising my bank details.