After reading the tutorial I can still not configure my Zyxel 2602H-61.
This is what I think it should be.
SIP Settings
Active SIP v
SIP Number
xxxxxx
SIP Local Port
5060 (1025-65535)
SIP Server Address
eu.voxalot.com
SIP Server Port
5060 (1-65535)
REGISTER Server Address
voxalot.com
REGISTER Server Port
5060 (1-65535)
SIP Service Domain
voxalot.com
Authentication User-ID
xxxxxx
Password
............ 
I have also try the eu.voxalot.com on the other places like the binary count from 0 to 7 but with no results. Maybe there is a time block after x try’s ?
Before this setting it was set for voipbuster and worked well.