In a Fortune 500 company, I'd imagine it could be quite difficult to definitively prove that they are not a customer of any one organization.
The company I work for is not Fortune 500, but we have several Fortune 500 customers. The amount of inane bullshit we have to deal with as a result is mind-boggling.
I recall an incident of large company paying whatever bill they receive and only to find out that they never had a contract with some of the companies and never receiving any service.
If it makes you feel better, it goes both ways; I once signed up for a utility, got service, and discovered months later that they somehow completed the paperwork to give me service but not to actually bill me.
I would bet this was sent out to a list that was put together that contained all of their "partners" which was in turn compiled from various other spreadsheets. Including one that had a 'support contact' column, or something like that and they assumed any that had that value was a partner. Over the course of the 6 years that the sheet has been cut and paste in various formats, they completely lost where any of it came from in the first place.
The company I work for is not Fortune 500, but we have several Fortune 500 customers. The amount of inane bullshit we have to deal with as a result is mind-boggling.