As far as I know, the only way to get a new number is to port one that you own from another mobile provider to 48, or to get a new 48 SIM under a new account (using a different email address if you're already a 48 user) and that will come with a new 089 number.
Why do you need to change your number?
If you need to contact 48 support about this then see the links in my signature below.
