i was required to pay my portion of a cardio scan a few years ago. when they asked me how much of the bill I wanted to pay I told them “all of it”. I left the hospital given potentially fatal (incorrect) advice about what activities I could safely engage in.
a couple of months later they sent me a bill requesting additional payment for the scan. I called them up and told them I had already paid for “all of it”. the finance lady shuffled some papers for a while then came back on line and told me to disregard the bill.