Does it just cost more on Sunday or why did I get charged 13.50 for my burger instead of 10.50

Did you get the salad bar

If you ordered the salad bar you pay more for that, unless you buy a meal that comes with it.

No, did you ask for additional toppings or anything not included or optional? If you have a question ask to see the MOD (manager on duty). They will make it right!