Can I unlock a Blackberry set up on AT&T network for use with Sprint/Nextel?

I recently bought a Blackberry Curve. I am with Cingular/AT&T right now. However my job I will be starting next month is on the Sprint/Nextel network. I have heard that Sprint doesn’t use SIM cards, therefore there is no way I would be able to unlock this for use with Sprint? Does anyone know how it can be done???
Does know the IMEI number have anything to do with it?

No. All phones are set for their carriers based upon chipset and cannot be changed except by a skilled technician at an enourmos price.

Kyocera Echo (Sprint) video tour – part 1 of 2

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