Allegiant Air Refused to return my money for a bag that I didn't put through baggage. Internet

Hello...When i booked two adult tickets online I inadvertantly clicked on a bag per person and so they billed two bags to my credit card, about $60.00. We only had one to put through baggage from the very beginning. We showed up with just one. I told them I thought I had checked just one bag on the website. I asked them to please refund my money and the lady said she couldn't do that at her ticket counter, which I thought was ridiculous. I called them as soon as I reached my destination in Plattsburg, New York. I was on hold for about 20 minutes before anyone came on the phone. I tried to explain this to the agent and she couldn't seem to help me. I want my money back for something I paid for and the airline didn't provide. I bet if I showed up at the ticket counter to put any extra bags through they wouldn't have a problem charging my credit card for that. I can't understand how they get away with this and I feel I was RIPPED OFF! I will not fly Allegiant Airline again. I'll drive to Orlando and fly out of OIA before I fly with them again. Return my money if you want me to ever fly on your airline again!