Incoming Calls

I have a Blackberry Tour thru Sprint. Everything works great EXCEPT half of my incoming calls start with a DIALTONE. After that total silence. Whoever calls me also hears nothing but silence. I have spoken to Sprint and Blackberry but no fix has been found. It seems like I am the only one having this issue. I have four phones on my account and the Blackberry is the only one with this issue. Sprint has sent me a replacement but the issue occurs on that one as well. In my opinion it has to be a provisioning or network problem but so far this problem continues. Has anyone ever heard of this or something like it? I'm at my wits end and may need to get rid of this unreliable phone and replace it with a Palm Pre. I have two of them on my account for family members and they have perfect service. My Blackberry is turning into a Raspberry.

I've been with Sprint for five years and I'm a Premier user. You would think that Sprint / Blackberry would do more to help but after three months all I get is finger pointing from both sides. The more I think about it the more I really believe it is a provisoning thing. I've asked Sprint to do a trace or some other diagnostic and I am really not being helped. I really want to keep this phone since it gives me everything I need when it works but the way is is being handled is driving me from Sprint and Blackberry.