Do anyone know a way to get actual Enterprise support and not get lost in tier1 for advanced issues?

We're an enterprise customer with 700+ seats, sso and the GTM addin is run through the office 365 console as a permanent addin to outlook.  And i have a handful of users where the GTM addin doesn't connect - it just shows up blank.  It happened before and then magically went away. It's a section of users who on my end don't have anything in common (some on vm's; some different type of office; none in the same departments or having the same other software installed on their systems)...  I spent 45 minutes last week with tier1 - call suddenly said something about leaving a message then i was disconnected.  No confirmation email of the support call; no call back after the disconnect.  This is not good technical support and there's seems to be nowhere on the site to escallate?