I had a collection agency contact me about a debt by letter, when I called to ask about making payments they demanded I pay the full amount. When I told them I could not pay all of the debt at one time they pressured me into giving a post dated check. When I saw I was not going to have the money in the bank I placed a stop payment on the check. I then went through my banks online payment and sent them a partial payment . I then got a call saying they would not accept the payment and I had ten days to pay in full. I cannot afford this, what can I do?