Hi I look after the SIP platform that MyRepublic voice services are being migrated to.
Your Phone number and password will not change as part of the migration of over the top SIP services. But they will need to register to a new IP. to facilitate this our DNS servers are returning the 2degrees IP's for the MyRepublic SIP FQDNs
Assuming an ideal SIP implementation and that you are using the provided DNS servers a reconnection of SIP will cause your CPE to do a DNS lookup and get returned the 2degrees IPs
This is the real world, at least I think it is, so this might not happen.
From what I have seen of the My Republic CPE dial tone does not mean you can place calls. If you can not ring out from your phone that is attached to your modem the best thing to do is to change the Registrar to sipres.2degrees.nz
its called Primary Registrar under the global section of Telephony on the Technicolor TG789vac v2
its called Registrar address under Telephone numbers section of Telephony on the TP-link VR1600v
Or rebooting it will cause a DNS lookup and fix the problem
I am happy to return direct messages here to help with your SIP line. Of note I can not fix billing etc. I just make things work :)
I will add anything else I find that might be of help here.
TLDR: the new SIP Registrar is sipres.2degrees.nz