We just encountered the same problem for a second time so I think it is a definite issue:
Callers from the Paihia/Russell exchange (403-xxxx) numbers are unable to get through to our VFX number. They receive the Beep-Beep-Beep-Beep (number unobtainable) tone.
The first report of this was back at the start of November, only 2 days after our VFX number was connected, so I thought it might resolve itself given a bit of time.
However, it is now 17 days after we had the service connected, so it looks to me as if the 403-xxxx exchange has not been setup to recognise VFX numbers.
Could you take this up with whatever organisation is responsible for the 403-xxxx exchange?