Tim Hortons review: overcharge on sandwich

I was ordering a farmers wrap meal for myself and a turkey bacon club meal for my boyfriend and the man serving me kept asking if I wanted to add things to my order that would cost more money such as add cheese or extra bacon and I kept saying no I just want it as it comes. He then asked me if I wanted the full size sandwich half size and I very clearly said I just want to one that it shows on the menu and he said okay so the full size. And obviously I believed him because he works there and I don't. However my boyfriend gets this sandwich all the time and has never had this problem. So when I got the sandwich back to my boyfriend he was shocked that it was so large and also shocked at how much I paid. It was over $20 for this simple order which normally costs much less. I was too uncomfortable to go back and speak to the man as we were already almost gone and I knew he would just blame it on me. It made me incredibly upset that he took advantage of me and went against what I very clearly asked for. I am hoping you can do something for me as I feel very upset.