<prompt> Human: I am a graduate student going to school in a different state from my regular Optomistrist. Since I had to return to school before Jan 1, I had to find a new one in my area to have an appointment to obtain more contacts since insurance had to wait until the first of the month.The appointment itself was fine. At the end, the receptionist convinced me to purchase a years worth of contacts for 152 including the 57 eye exam copay. My original intention was to only purchase the required eye exam and 6 months of contacts, which came out to 65 after insurance. I was planning on taking my prescription and purchasing more at a cheaper source online. However, she told me that the year was a much better deal since insurance will only pay once per year toward contacts, so I caved in to the 152.Now, over a month after my appointment and receiving my contacts, the receptionist who had rung up my insurance information told me that she made a clerical error in charging me and that I owed them 40 more for the year of contacts. I kept telling her that this was deceiving because I wasnt even originally going to buy the year and kept asking for clarifications of the various charges. She kept sounding personally offended and acting like I should feel sorry for her. Keep in mind this is a month later. I just looked up the place on Yelp, and all the comments seem to be negative comments about this particular receptionist and ways that this place has scammed them.I told her that I would call back because I was calling her during a break in the middle of a class. I know that 40 is not that much, but I am a poor graduate student, and 40 usually covers more than a week of food for me in my budget. What are my options? Ive been told by someone to just ignore it but could they send someone to collect from me? Would not paying affect my credit score somehow? What is morally and legally the correct thing to do in my situation? Any advice, particularly if you have been in a similar situation, would be greatly appreciated.  <response>: Yup, thats a no - you shouldnt pay this. You agreed on a price, they sold you the goods for that price, thats the end of the transaction. The fact they made a clerical error is THEIR problem. 