Bit of an odd request. Why do you want to do that? You could just get a new SIM and register it as a new account etc. But if you want a new 089 number on your existing account so that you retain your membership/account balances etc then you'll have to contact 48 support and ask them if they can do something for you. See the link in my signature below.
Hope this helps.
I am not a 48 employee so if you need to contact 48 support then use option 3 or the chat facility here.