50% of message allowance used--on unlimited texting plan?

[Bewildebeest]

Pretty much what it says on the cover.  I have an unlimited texting plan, but I just got a text saying 50% of my text message allowance has been used.  Granted, this isn't much of an issue, since it's for the billing period that ends tomorrow, but still.

Wha?  How does unlimited mean 1000?