<prompt> Human: In November 2013 I visited a Medical Imaging Center on two separate occasions. The first time I was billed a 30 co-pay but the second time I was told there was no charge. A month later I received an invoice for 30 and when I called they told me the staff made a mistake and I DID have to pay. I refused and that was the last I heard from them until yesterday when they called again and threatened to send me to collections. 30 is no great hardship for me but I dont think I should have to pay for their mistake. The last thing I want is a collection agency pestering me, do I have any recourse here or should I just pay the 30?  <response>: Personally, Id pay it and let it go. Its not enough to get into a debate over, and certainly not something you want held against your credit score. Youre in the right, but does it really matter? 