It's not the provider's responsibility to help their customer get their sh#t together.
That's a problematic customer you don't want unless you're otherwise broke or want to keep them for other reasons (e.g. publicity).
The time this happened to us, I was pleased the company looked at our website and phoned the receptionist. We paid the bill within an hour, and moved the responsibility to the finance and IT teams.
Maybe there are too many customers who just ignore bills for services they no longer want to use, I don't know, but given these companies usually have a sales team it would seem worth the time to make a call or write a personal email to an existing customer to maintain their custom.
You are telling me:
1. Microsoft should have tried to find a different way to contact and reach out.
2. That you would have moved your eMail/Groupware to someone else because of that.
To each their own.
If they can pay, then just pay for the service they got.
Seems pretty straightforward.
The ones that contact support for every little thing or those that have a million strange feature requests on the other hand.
Maybe they sent all the extra invoices? It sounds like you are assuming discontinuing the service was the first and only thing they tried.
It seems like Mozilla has made quite a lot of errors in the past few years.