How to change shipping from UPS to USPS on an item that has already sold

[veckna]

Hello;

I have sold an item last night that I orignally planned on shipping with UPS ground, due to the size of the box.  The item ended up being bought by someone in Hawaii, and the UPS shipping charges are twice what the USPS charges would be.  When I go to print my label through ebay like normal, I am instantly taken to the UPS website.  It seems like I no longer have the option to use a different shipping company like you normally do when something sells.  By listing UPS as the shipping method on my listing, it appears I have locked myself in to using only UPS.  

Now, I could go straight to the USPS website, load up the information, and print a label, and then upload the tracking # to ebay, but typically, when you use USPS on ebay, you get a decent discount on the shipping fees.  I can't get that discount by going straight through the USPS site.  

So my question is, is there a way that I can add USPS back to my options as a way to ship this item?  

Thanks.