Bad services

I had an arrangement with ssda that I will make payment in two installments and the balance was less than R2000.I paid the first R500 last month and today an amount of R1500 then I received miss call and call back.Then the agent tell me I owe R1700 which I did not know Ssda did not even send me communication about this. When i then said to the lady I want to speak to a manager then told me I must call on Monday , I then said it's not possible that someone is not available then she rudely drop the call this matter happen at around 11H45.