You must only call people who are not on the Federal list or who already have a business relationship with you. If they contacted you in some way you can legally call them for 13 months.
Go to www.donotcall.gov to register and get info. If you don't register as a telemarketer and you get a complaint...you're screwed. And the definition of a telemarketer to the government is anyone who makes ANY calls to a residence in the course of your business.
Just to clarify, for personal phone numbers, you have 90 days that you can call them if they contacted you. You have 18 months if they have done business with you in the past.
If they ever ask you to not call them anymore, you have 0 days, regardless of why you have their number.
It's free to register for up to 5 area codes. Makes it pretty easy to stay compliant.
Dan