I have a user who has a 8700c that will randomly dial a phone number from someone in her Contacts. This has occured when the BB was placed on her desk unattended and after she has replied to an email etc. This has happened while in the holster and out.

Has anyone else experienced anything like this ?

Nope, we have tons of 8700's and nothing like that. Maybe wipe out the handheld and reinstall the OS?

Was a Bluetooth headset connected at the time it happened, or was Bluetooth on?

Bluetooth was on but headset was not connected

Well, turn if off for a period of time, and see if you get the same results...