As you may have come to realize this is more of BroadVoice issue than anything else.
As per
MySIPSwitch Community Forums :: View topic - Does MSS work with Broadvoice? it seems that this is an issue that goes beyond simply VoXalot....
My suggestion:
-Erase all instances of Broadvoice in VoXalot and MySipSwitch
-Set it and register it at PBXes (forwarding calls to VoXalot)
-Set up PBXes as an outgoing-only provider in VoXalot, allowing you to make calls via BroadVoice in return