I need help resetting my authenticator but Microsoft Support goes in circles.

I'm in an uncommon situation where my Network Engineer is terminated and therefore we have to go through the Authenticator dance across many of the web portals he has had access to. I talk with the web portal vendors and we are able to get through the process of decoupling his Authenticator and transitioning administrator access over to me.

With Microsoft it's not so easy. I have Global Administrator access to the tenant but never logged in. As I do not remember the password, the ability to reset it is not registered so it requires that I "contact support". When I call in to support it tells me I need to go to aka dot ms slash support. I go there and I fill out the forms using a Microsoft account that is bound to my main tenant (I have 4) but of course they will not address my concerns when attempting to gain access to a different tenant other than the one I'm submitting a case from.

I really don't know what steps to take here. I've been going in circles here and just need a human being from Microsoft to pick up the phone and help me get this reset so that I can manage my tenant. Anyone had any experience or can offer constructive thought on how to address this problem?