Overcharging according to state statutes- help

Hello...I contacted Sonic Cash (internet company) and informed then that according to Kansas statutes, they are overcharging my finance fee. I asked them to refund anything over the maximum fee and apply it to my loan balance. I received the following response:

When you requested the loan with us you signed an agreement that stated you were taking the loan out under Idaho laws not Kansas laws.

Huh? If I don't reside in Idaho, can they do this?

Thanks.