How to turn off shipping options

I fixed this problem a couple of week's ago, and need to do it again on another ZenCart store, and can't remember how I did it. I've searched the WIKI and the Forums and can't find a solution. Can someone help?

I am using USPS shipping - which is working fine. But we are giving Free Shipping on orders over $25. That is working OK, too.

Here's the problem: When Free Shipping kicks-in, I want to remove the option for the paid USPS shipping. I know there's a way to do it because I did it before, but for the life of me, I can't remember how.

Thanks

In the settings for Modules ... Order Totals ... Shipping ot_shipping is an option for Free Shipping on orders over XX.XX ... this will override the other shipping modules when it triggers ...