Wirelessly posted (HTC Diamond: Mozilla/4.0 (compatible; MSIE 6.0; Windows CE; IEMobile 7.11) Sprint MP6950SP)
I recommend using the sprint shipped rom or a custom 6.1 rom for maximum memory, compatability, and stability.
I would use either Skype or Nimbuzz for the calls. Both should work.
Bluetooth should work if you have a decent connection and pairing with your device is solid.
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Good Luck To You!!