Lack of comunication

I have made payment arrangements to pay back my credit card with Standard Banks Card division. I am currently Unemployed and is freelancing as I am not able to find a job. Twice now I made arrangements with the bank to pay a specific amount back each month and I was told that is what I need to pay back. Now I have the bank phoning me and telling me that I am in the rears with my payments and that there is no agreement loaded on there system to state that I will be paying them back R1000 per month. Because I am freelancing I can not guarantee my monthly income.