When does an account go to credit?

I received a call from Superior Asset Management last week about a water bill that fell through the cracks and was sent to collections by the county. The rude collector called me and asked if I was aware, as they were updating credit and wanted to make sure I knew about it. I asked her if it was reported to credit yet and she said yes, I told her I didn't want to deal with it now, she got mad and said it would ruin my credit and they were going to do an employment verification on me.

I pulled my credit today and I do not see they have reported anything as of yet. If I were to send them a payment via certified mail, would I have recourse to have it remove any future reporting to credit? As long as I have proof of payment in full, would that be enough to stop them from reporting, or can the report any time, even after payment in full? For instance, the receive a collection account in June, I pay in July, and in August they report as a collection account, then September they show paid in full?

Thanks for any help...