I have done most of the phone deals over time. Though I too have had problems with Sprint, I found that a call and then asking to speak with a supervisor usually does the trick. Also if they say that your account does not show you were signed up for the special offer tell them that a telemarketing rep promised you this offer. It is very difficult for them to authenticate and they usually give in.

Sprint is FAR more accodating than MCI in my experience though neither is perfect. Good luck and let us know how it turns out.