Unfair deduction

I had a loan with bayport I think I 2010 so they garnished my salary for R10400 and I paid it till it was a 0 balance. Last year they garnished my salary again for R3800 and yet again I paid. This year however they come back to garnish me yet again for R2500. I called their call centre and they've transferred me to their legal department and they told me I just have to pay this loan. They just made their last deduction on my salary last month and I'm getting irritated as I know they going to do the same thing over and over again. Can you please advise me what to do because I made a loan for R8000 and end up paying for the rest of my life