Devastated and Frustrated over rediculous T&Cs

Last month i was offered a settlement amount to settle my ACKERMANS account and the money they offered to me over the phone was different from the amount they sent to me via text with their banking details(the quote over the phone was less)... but i paid it anyways and was R1.91 short on the settlement and they said i am still owing so on Monday the 30th of August i paid R5... now they say i still owe R500 because the settlement was not paid at the same time and they have terms and conditions that change every time i call them which were not mentioned the first time i spoke to them... when i called in and asked to speak to a manager i was told that the manager is not available and a call back will be arranged my phone rang twice and call ended so i could not even answer that call and i keep on getting calls from them and texts asking me to make arrangements with them... i asked them to listen to the first call recording but clearly they have not and i have sent them emails asking for a paid up letter and theres no reply so i assume its because they say i still owe them............... i want them to listen to the first call recording and send a copy to me because i am not paying that R500.... then reverse the money i have paid them i will pay them which ever money i can afford because clearly the settlement was a bad idea....