Make sure that you have told Sprint to pass the ANI information on the outgoing calls. This is a question that the two providers I have dealt with recently have asked me. Make sure that you have gone into CHA ISDN PUB to setup your DID information to be passed thru correctly(if you would like the DIDs to show up individually). If your T1 is setup as ISDN, make sure that on page 2 you have "Send Calling Number" stroked "Y".
It's hard to say that the T1 must be setup as ISDN in your switch. My T1 with AT&T is setup as "TIE" and my calling information goes out just fine. But I am not an expert on the subject, so this is just my two cents.