Hi Katie. I kicked the crack habit and I have several friends who have kicked the crack habit. But I know many many more people who have not kicked the crack habit. Your son will quit when using crack causes him more pain than not using. It's a different bottom for everyone.
I know that it's hard when cracked up loved ones called. Next time, maybe don't answer the phone. Let him leave a message and then choose whether or not you want to call him back later. Nothing is going to change for him until something changes - and that may mean mom and dad cutting off all contact. You can still have hope without contact. Actually, in my situation, I find it is easier to have hope with no contact.
Hang in there. This is your son's battle. Do you have other children who don't smoke crack, abuse you verbally and steal from you? Maybe spend extra special time with them instead of spending your energy worrying about some-one who doesn't want help, only hand-outs, right now.