What can I do

A number of years ago I aquired a debt with a bank. A couple of years later a collection agency called about the matter. I set up a payment agrangment but was unable to follow through because of unemployment. I have yet to aquire a job and my spouse barley does enoughto make ends meet as well as pay her student loans. Earlier tis summer I made new arangements with the collection agency and even made one of 4 216 dollar payments. However, my income took a dive once agian and because of this I am unable to pay the 216. I can pay 50 or so and have sent an email stating this but have revieved no reply. I would call but every time I do i am treatened with law suit unless the debt is paid in full or i make huge mothly payments like the 216. Can they demand the higer payment or can i stop any suit by sending what i can.