set up payment now email says it is due

I called in a few weeks ago, and the very nice rep set up my bill in two payments, its an extremely high bill, as always- One payment was due yesterday, $401.13- which i paid- and the other payment was pushed to March 8th. I paid the one due yesterday, and now got an email saying the 3/08 payment is due today. I am waiting on a tax check is why she helped me set it up that way.