Thanks for that interesting explanation affinity. I'm going to remove the registration on one of my accounts that I never use for incoming. I just put it there coz it has an incoming number, even though I never use it!
I tried PBXes before voxalot but it didn't work coz they had already been blocked by Betamax. So I would suggest to anyone with Betamax as a provider, who doesn't have an incoming number in use:
SET SIP REGISTER TO NO FOR ALL BETAMAX PROVIDERS (VoipDiscount, VoipCheap, VoipBuster, SipDiscount etc etc).
otherwise voxalot might get blocked by them too