CHANGING IP (Urgent)

I am a gamer and if anybody that plays video games knows that ip grabbing and ddosing is a BIG problem in video games. My ip has recently been grabbed by a person in a community discord. This person has been non-stop ddosing me. I've tried everything to try and change my ip. (Hard reset, soft reseting router) I have xfinity as my provider and they tell me I have to contact the modem company that we used. If anybody can help it'll be great appreciated.