hairy1: You might be better off trying to port a "real" number to get around these sort of issues. I had a few problems with my VFX allocated 09926.... number until I ported my real Pukekohe 09 238... number when I was with VFX. 2talk were good with my number port. It took about a week. If you have telecom number /edit account/ you can customer link a local telecom allocated number then port it to 2talk.
Cheers,Matt.
For what it's worth the 2Talk numbers are real numbers I have a 0 9 280 xxxx number