Changing default USPS mail types

[JonesOrganicTea]

Hi--

I can't figure out to how set our Shopify default mail type to USPS Priority First Class PACKAGE, not Priority Mail. Somehow some of our orders occasionally get pegged as mail rather than packages in Shopify, and when we don't notice it in time, we get packages returned for additional postage.

I've looked in the shipping settings and am not finding a way to set Priority First Class Package as the default type. I've looked all over the help site and can't find anything, and there seems to be no way to contact Shopify Help directly anymore!

Can someone help me fix this?

Thanks!