Missing 5 RP

Hey guys, I currently have 482 RP, and I want to buy the Cho'gath skin that on sale right now, which costs 487 RP. If you were able to do that complicated math, you will realize that I am missing 5 RP. I have friends telling me that I can send a ticket asking Riot for the missing RP. Is this true? If so how do I do that? Thanks -Near