Kramer & Frank, P.C. Debt Collection Complaint

Kramer & Frank, P.C. Debt collection department,

Credit card False statements or representation Attempted to collect wrong amount Missouri

I had a credit card with - - back in - and I lost my job so I was unable to pay the debt. In - I received a garnishment from Frank & Kramer for $1400.00 that I paid in - for $1800.00. I never received a summons to go to court on this, but I paid the bill because I knew that owed - - $500.00. I received a garnishment in the mail today -/-/- for $1200.00. I called Frank & Kramer and they claim that owed an additional $1300.00 in post judgment interest and told me that this payment has to be paid and that I don/t have a choice in the matter. I should not have to pay $2500.00 in interest to a debt collector on claim that is past the statue of limitations and that I have already paid. How can I be sued for a claim that I never received anything from the court tot appear on this claim. Please help me.