Because your number would not be native to your new exchange, and hence the exchange can not support it. Call 123 and ask them for yourself.
nzbnw
can telecom accept requests for 09950xxxx (vfx auckland numbers) to be ported to them or can only numbers which were initially issued by telecom be ported back to telecom? and is this the case for all exchanges or only some?
Trusted
... 
