Beth:
Good for you for wanting to stay away from it! That "dealer" isn't a "dealer" - he's a pusher! But whatever you want to call him, it's awful.
If you really want to not be contacted again, change your number - I know it's a pain, but it works.
Is this a home phone or cellphone? If it's home, get call blocking and block the number via the phone company - he'll get the hint hopefully. Also, report it as a harassing phone call whether it's a home number or not. That way, you won't be able to call back - because once you report it, you can't call without getting in trouble.
You could also anonymously turn the person in - just don't tell them you will.
I did that with my husband's dealer.