Originally Posted by rowan

As far as I know this is all you get...

1) user/pass
2) your secret
3) action: add/rebill/cancel/delete
4) the price of the transaction
5) the transaction number (I think?)

Verotel said they were redoing their system a couple of years ago to include custom vars but that never seems to have happened.

It's still worth asking them, perhaps they have implemented something now.