Harrassment at its best

During 2014 I was unemployed for about 4 or 5 months.. I made financial arrangements with electric express which they understood at the time ( Keep in mind that I might not have paid my full instalments for those few months but I definitely paid money on those accounts during that specific time), Anyway I have had a permanent job ever since and I have been paying R800 some odds on my R678 some odds original instalment.. The JD group has called me every single day DEMANDING payments (which they have been receiving every month), Disturbing my 73 yr old gran on her landline all day every day demanding to speak to me when I asked them to remove her number. Last year I increased my instalment to R1100 because they kept demanding and now I still have them calling me demanding money for a phone which is broken by the way????!! I am paying on time.. I am paying MUCH more on my monthly instalment, I have one or two months left with this disgusting company, So what more is it that I have to do? Demanding calls and threatening smses?? Since I have taken out an account with electric express it has been nothing but a nightmare. I have never been more disgusted in a company, Worst service EVER