Microsoft is really not making any effort to make Azure intuitively accessible. Never seen anything like it. And Azure customer "service" completely ignores you even when you're on the full trial (and you'd think they might want to impress you) and the Translator help desk ignores you for a month and the replies something like "I'm assuming you solved this issue so I'm closing the ticket".
I have not reached the 2m character limit yet but neither do I believe I will be charged. As I understand it, there is still a free tier (not the same as free trial) and because things are not confusing enough on Azure, they make you sign up for the Pay-as-you-go plan in orfer to access the free tier. But according to this page you will not be charged as long as you don't upgrade from the free tier (S0) to the S1 tier (which they also call pay-as-you-go, just in case someone was starting to make sense of things): thid is what it says:
What happens if I exceed the transaction limit on my Free tier for Text Analytics?
Usage is throttled if the transaction limit is reached on the Free tier. Customers cannot accrue overages on the free tier.
Of course, there is still a chance that this information is wrong, in spite (or because) of the page being managed by Microsoft, but that is as much sense as I can make of it at thi point.