Harassment

I hope this gets to the right people, I was desperate fr a loan this people, came to the picture, i agreed to whatever nonsense they promised, then later not hours, but few minutes i called to cancel the deal with them, i was assured they wer not gonna debit me, but unfortunately they couldn't wait, to debit my account, i made a reversal to it, that's when I started receiving demands, from their so called collections department, i responded the email, that the has to be a mistake, since i cancelled the deal on the same day, but it fell on closed ears/eyes, they refused to listen to me,so for the last time, i cant be charged for something i have never used, not even for an hour for that matter