Car insurance help

My insurance was due on the 16th but got an extension until the 25th because my car wouldn’t crank took it to the shop and they said it $600 worth of work (it’s an 2005) so I’m using a friends car until I get my loan (Dec 20)to get a another car how I do I cancel my insurance but I still wanna use them when I get another car I’m 18 and don’t understand my classmate said just don’t pay it but I’m pretty sure I’m supposed to call them