I Am Frustrated and Confused

Recently I am being frustrated by one douche bag..I know this guy bcoz he is my friends school buddy. I never met him..I just saw his face in their school photograph.He knows me bcoz my friends tagged my photo in whatsApp.Recently he started to use my name to make his girlfriends feel jealous..saying to them that he likes me..by saying so they feel jealous. The worse part is that one of my best friend is his ex-girlfriend.She`ll laugh saying that he likes me..and he thinks that he can make her feel jealous by saying that he likes me..This has become an routine now.But they don`t understand how I feel..It is really frustrating and annoying because in their chaos I`ve been made a fool..Just a piece of joke or thing that entertains them..A guy uses a persons name just to make his ex-girlfriend feel jealous..I don`t know what to do..I don`t even have his number or any contact info so tat i could warn him not to use my name..Pls help me with this situation..I need help..How can I get rid of this crap..