You won't be able to do this without the assistance of your IT department.
Your BES account is tied to the PIN number of the device... currently your 8700.
You need to do a new Enterprise Activation on the Pearl, so your BES account will then be assigned to the new device.
Your IT Department needs to set an Activation Password for you.

Also, you're knowingly doing something that is frowned upon by your company.
That's just stupid.