I doubt it has to be 159 on an Option 11, but I do think there's a specific range it needs to fall into. I also highly doubt it can be "changed" from a 500 type to a phantom...

I work with a phantom loop on an 81C that's # 156.

[Linked Image from web.atcomsystems.ca]
Looking for a VoIP Phone Canada provider? Put Atcom's valuable VoIP expertise to work for your business today!