Day light *******

I have account with Markham's, last year June my monthly installment was somehow around R400 and some odds... all of a sudden boom! the installment grow to R750+... And then I called in to find out, Okay we came to arrangement that I can afford, since I couldn't afford the R750+... Then they call me more then 5 times a month while we have arrangement and charge 1 call R20+ and email me 3 times per month which is R20+ and the interest fee on top of that... all in all it goes back to the amount that they said I can pay monthly of which is the half of the installment.