My cell phone has been cloned! My provider says only way to stop is to change my number, is there another way?

Someone borrowed my cellphone %26amp; I found out that it has been cloned. I receive all his calls and he uses my cell plan and my provider said my only option is to change my number. I really need my number and do NOT want to have to change it. Does anyone know how I can get that idiot off my phone without changing my number? HELP???My cell phone has been cloned! My provider says only way to stop is to change my number, is there another way?
umm, this is a unique situation...but i think this is worth getting authorities involved