False Promises and no accountability

I was minding my own business when a lady from Ucollect called me and offered me a loan and because of the deal that was on the table I could not resist and accepted the offer and we even captured a debit order mandate on my banking app on my phone, the lady said she would call me back and that never happened. The following day I called and spoke to another lady which unfortunately didn't get her name as well and she said she will investigate and get back to me and 2 days later still no one called me back, then I called in and the lady I spoke to referred me to their head office which I called and to my surprise told me that they do not have my details on systems and know nothing about my application. I then called the call centre again and spoke to another lady who put me through to her supervisor by the name of Nicole and Nicole promised me that she will follow this up for me and I should call her back the next day if I do not have feedback and this is exactly what I did and I was told Nicole has left for the day and again spoke to another supervisor by the name of Bonita and she also promised to follow this up for me and again she also never called me back and when I do call asking for Nicole and Bonita I am told they are busy and they will call me back, I have left countless messages for them for a week now and still no feedback, so I am no longer interested in the loan, all I need is for someone to help cancel this debit order mandate on my account because clearly no one is interested in helping me, we barely have a relationship and already we having problems. Can I please get someone to assist me with this ASAP.