Finding 0800 number supplier

Hi

Just posting here as Vodafone is our main Telco supplier.

We have an 0800 number that was setup here before I started that we want to put a divert on to a mobile, no one here has any record as to which Telco it is setup with though, I have checked with Vodafone, Spark, Vocus and 2 Degrees, but they all say they have no record, our accounts department have no record of whos paying for it either.

Any ideas how I could figure out which Telco it is with?

Cheers