How to change my BBM service?

I have unfortunately broken my iPhone and are currently using my brothers old blackberry, and I have all his BBM contacts, name, pm everything, but somehow when I delete a contact it deletes it on his current phone, whenever I change something on his old phone it changes it on his new one too? How do I change it so it doesn't do that? And we can both have separate BBM?

All answers are helpful, thanks.

Reset the whole blackberry with Wi-Fi off.

Best to get a new Sim Card and then security wipe the phone you'll find this in settings, hopefully that'll work.

For BBM - You can't

BBM ID is the 'phone ID' not your personal ID (name or account)

The email etc, yes. But not BBM
that is tied to the Blackberry Hardware ID - the 8 digit number of the Phone.

if you have the same email etc,
then sounds like you have not set up a new Blackberry account
you need to talk to yoru network and then ask for a Blackberry internet plan (not your normal internet from the other phone), Then they will reset the phone and attach it to your account.

You can then login to the blackberry web page for your provider
blackberry.xxxx.co.uk (where xxx is your network name)
register the Hhomework ID (8 digits) to the your phone No.

Oh, and your brother needs to tell his provider to unregister it from his account also.