Russells harrasment and reckless lending

I was offered an R15000 furniture account from Russells furniture stores on a R5000 salary. I then bought 2 laptops and started to pay my account as per our agreement. I was then in between jobs and explained this to them. I have been making payments less than the instalment amounts due to affordability and yet they continue to harrass me every single day while they are receiving payments from me every month. I feel like I was recklessly given an account of R15000.00 by Russells on a R5000 salary. Now I cannot afford to pay the full instalment amounts and have spoken with them saying I will be paying R50 per month onwards until I can get out of debt. They continue to harrass me daily after recklessy giving me an account of R15000.00 of which was not affordable for the amount I was earning. I am still paying them every month but cannot afford the full amount but I am being harrased daily by their rude call centres even though I continue to pay them what I can afford. I have also expressed this to them numerous times. I feel this is reckless lending and a violation of my rights as a South African who is actually paying my debt every month.