1) Auto Provisioing -  Astra phones

[Currently not supported until further notice]

2) Manual Provisioing -  Astra phones

Step 1 - Sip Account Settings: Please see the screenshot below.

Step 2 - Set the dialplan to:
[2-9]11|911|[2-9]xxxxxxxxx|1[2-9]xxxxxxxxx|011x+#|xx*|*xx+#|xxxxxxxxxxxxxxxxx#

Step 3 - Reboot the phone