Hi Uncle, I was in US for a holiday and fell sick during the trip. I went to see a doctor in a public hospital. I paid a deposit of US$3k and they told me if any refund they will mail me a cheque, if the deposit not enough they will bill me again. I recently got a call from their agent asking for further payment. I have received the detailed bill from them and actually think that they are overcharging for very simple medical service. Do you have any advice on how I can dispute such bill?

You may wish to check with American Medical Association website to see ascertain whether the charges are reasonable.

http://www.ama-assn.org/

If you have evidence that they have you may right to the doctor to claim the refund.