On the phone, select
Tools → Settings → Connection → Access points. Without a configured, functional AP your phone won’t be able to connect to the internet.
Now, to configure the phone itself, the following settings must be made:
Tools → Settings → Connection → SIP settings
Profile name: VOIP Connections
Service profile: IETF
Default access point: (Pick your access point from before.)
Public user name: sip:<username>@nyc-02.mypbxmanager.net
Use compression: No
Registration: Always on
Use security: No
Tools → Settings → Connection → SIP settings → Proxy server
Proxy server address: none
User name: none
Tools → Settings → Connection → SIP settings → Registrar server
Proxy server address: nyc-02.mypbxmanager.net
User name: <username>
Transport type: UDP
Tools → Settings → Connection → Internet tel.
Create a profile with a name of your choice, then associate the SIP profile created earlier with this. This will set up one profile which can then be used to make calls across the network via VoIP.
After this, set your new VOIP Connections profile as the default via Tools → Settings → Connection → SIP settings → Options → Default profile.
With these settings your phone will always connect to the AP whenever it is found and register with the VoIP server. It will then be able to make and receive calls. Setting Registration to When needed makes the phone prompt before connecting to the AP and the SIP server when an attempt to dial an internet call is made. Inbound calls will not work in this case.