Any of the following SIP Adresses should work:
123456@voxalot.com
123456@xx.voxalor.com (where xx is us, eu or au based on the selected prefered cluster)
*010-123456@sipbroker.com
Now the fact that calls are not coming in but going to VM makes me think you may have an issue registering to VoXalot (keep in mind that you do not to be SIP registered with VoXalot to call out, but you do need to in order to receive calls).
Call one of these
Access Numbers ( that is local to you) from a regular landline or cellphone, When prompted enter *010-<Your 6 Digit VoXalot number># .
Does this call ring your ATA?