Here are some notes for SIP providers we have come across in the past.
The fields surrounded by red below are the relevant settings.

sipgate.co.uk
| Registrar (proxy) | sipgate.co.uk |
| Registrar Port | 5060 |
| Service Name | “SIP-ID” from Telephony / Phones section of sipgate.co.uk portal |
| Register to Receive Calls | Yes |
| Domain | Leave Blank |
| Phone Number | Leave Blank |
| Username | “SIP-ID” from Telephony / Phones section of sipgate.co.uk portal |
| Password | “SIP password” from Telephony / Phones section of sipgate.co.uk portal |
| Authorisation Name | “SIP-ID” from Telephony / Phones section of sipgate.co.uk portal |
| Register Interval (seconds) | 60 |
yay.com
| Registrar (proxy) | talk.yay.com |
| Registrar Port | 5060 |
| Service Name | “SIP username” from Users section of yay.com portal |
| Register to Receive Calls | Yes |
| Domain | Leave Blank |
| Phone Number | Leave Blank |
| Username | “SIP username” from Users section of yay.com portal |
| Password | “Password” from Users section of yay.com |
| Authorisation Name | “SIP username” from Users section of yay.com portal |
| Register Interval (seconds) | 60 |