And if you do indeed have the required BlackBerry data plan, when you send a request for someone to be added to your BBM contact list they have to accept your request. It will stay pending until they accept.
Sometimes PIN requests just don't seem to go through. You might have to delete the pending request and resend it. If it still stays at "pending" and the other person has not received it, have them send the request to you. I've had this solve the problem on occasion.
Call your carrier and ask for a Blackberry data plan. A standard data plan will not work with a blackberry. All you will get is phone and text. No BBM or other internet use.