harassment , debit order cancelation

After telling them im unemployed currently looking for work they tried debiting my account for the full amount resulting in a R150 charge for a debit order that didn't go through ive been paying them what i have they call me every single day each time its a new person and i have to explain the whole story over again i had to cancel the debit order through my bank because i couldn't afford the R150 every time time the debit order doesn't go through i explained this to them so they still put it through anyway