To call a Betamax ID from Voxalot, you may have to use a different approach, using a rule in your dial plan, as described below.
Set up a rule under the advanced mode as follows :
Priority* : Your choice based on the other rules already set-up
Pattern* : _400 (Just an example, but can be any number you prefer)
Comment : Call JohnDoe via Poivy
Replacement* :
johndoe@sip.poivy.com
Provider* : Poivy (or any Betamax provider you have set-up)
Active* : Yes
Virtual Toll Free Enabled* :No
ENUM Lookup : No
Geographic Lookup : No
To make the call : Dial 400# from your Voxalot registered phone.
I just checked this and this method works.
Post back if you need further clarification.