If his number is showing when he calls you can call customer service and have them block it. You can have up to 5 numbers blocked at no charge. It's called nuisance blocking.
If he is texting you too you'll want to add usage controls and block his number from calling and texting. This service is $4.99 monthly and you add it via myverizon online.
If it's restricted you would have to change your number or contact law enforcement and possibly pursue harrassment charges cause Verizon can't block restricted numbers at this time.
Hope that helps
