User assignments and changes should be able to be tracked from analytics portal.
In our enterprise company with several admins and a few super admins it can be frustrating tracking down what line moved to what device and which admin made the mistake.
Recently I had an issue that appeared to be users being removed from a device and added to others and there was no data in the portal to show when they were changed. Tier 1 support couldn't even find it on their backend systems. At least give your agent's the ability to see all changes to an account, they are very good agents.
I believe documentation of user line assignments would assist users and support in tracking down and troubleshooting issues. This would have prevented me from reaching out to support or if I did not see that, the support agent could have walked me through and had first call resolution.