I have an unlocked 7130g on Orange BIS and am thinking of getting an unlocked 8800, can I just do a device switch using dm, or do I have to contact Orange to release the old phone and register the new one, I will be using the same sim.
Thanks.

In the BIS page for Orange, there is a "change device" option.
Here you change the PIN and /or IMEI of your current device with the new device.
This will then send service books and setup email accounts on the new phone.

Device switch in DM will transfer stuff like contacts, calendar, messages etc. and is advised you do that, or a backup from old phone to restore on new phone.

Another way that you can switch to the new device is: on the new device go to the "personal email setup" program. Log in to the BIS using your old log in information. The BIS will recognize you have a new pin and ask you if you want to switch to the new pin. Answer yes and the BIS will release your old pin and assign your new pin to the email accounts you have setup. A couple mins. later you will be receiving emails on the new device.

I prefer to do it this way and then reinstall software individually. I sync my address book through google sync, so I just install this first and it downloads all my calendar and contact information.

Thanks guys, I will give it a go.