I don't want to help pay the monthly family phone bill
Well, tell me why you don't want to help your own family with the monthly bill?
I tell you they are scum of the earth
I understand that you might have issues with your family members, but you should pay your share of the bill, since you use it as well. It is wrong to avoid paying like that, especially to your family. I think you should keep your financial obligations, no matter the personal difficulties you might have, otherwise you become the bad person in the family.
I will cut them off so they learn to get along.
This doesn't help anyone to cut them off, because you will suffer from it too when you can no longer use your phone. Giving money for something that you use is considered important and it will be a bad look if you don't help out.