First, you need an XML with all of the contact info as per the link in my previous post. I'll paste an Excel file with a script that I found which can make these for you. Once the file is created, rename the file from "xxxxxxxxxxxx-directory.xml" to "000000000000-directory.xml"
https://community.polycom.com/t5/VoIP-SIP-Phones/Create-a-directory-XML-from-Excel/td-p/75143
Second, you upload the file to somewhere the phone can pull the file from, an FTP server or the like.
Third, you set the url path of the file without the filename onto the "Custom Contact Directory URL" field in Device Settings within Monster. I'll paste an example below.
If your URL is as follows,
cfg.files.com/client-name/000000000000-directory.xml
Then this is what you'll paste onto that field,
cfg.files.com/client-name/
We had horrible luck with the Panasonic TGP phones on 2600hz (even though they worked fine with another PBX system), and 2600hz support said they don't officially support them. We switched all of our clients to the SNOM M325 and haven't had any issues. I know that isn't the answer you want, but, just thought I'd throw that out there!
You definitely don't want to mix the two together! Use 100% SmartPBX or 100% Advanced CallFlows and Advanced Provisioner.
They're both APIs on top of the same underlying system, and SmartPBX is meant to do a lot of things in an easy format. So if you go in and change something underneath it, weird things will break.