You cannot alter the Teams interface page, but partners (like Crestron..whom I work for in full disclosure) have the ability to put in a page flip to a custom page interface. Through that interface you might be able to put in a call.
One suggestion that worked for a customer that I helped was to make a user called IT HELP DESK that is in your AD and that user could then be added or the new meeting button would be there to find them. The customer that I helped put a table tent (and a poster on the wall) in with the instructions on how to dial for help. It worked pretty well for them, but just figured I would suggest it.