Refuse to settle account

I am trying my best to settle my debt with Mr Price( ACS). They refuse my offer over 3 times now and I am offering 60% of the very high interest amount which is more than my limited that I have used. I am in financial difficulty . I am trying my best and I really can't offer more. I even try to pay an amount monthly that doesn't seem to have any effect. Never Ever am I even buying any clothes there. They are greedy and insane with their interest. Clearly if you don't have you don't have. High interest rates and non stoppable calls don't create money unfortunately.