As per my previous posts, I use MyNetFone as my SIP provider and I run a Raspberry Pi with RasPBX (which is FreePBX for the Raspberry Pi ready to install/tweak and configure).
Below is a quick run down on how you can configure your SIP Trunk for MyNetFone on this device, which is working for me currently.
Trunk Name: mynetfone
Outbound CallerID: [configure based on your 09nnnn number or your DID if you have one]
Trunk Name: mynetfone-sip-out
Peer Details: (as below)