You know what? I did not set up the original shipping and I don't know anything about the original shipping. If you didn't pay for overnight shipping (which you didn't) then you aren't getting overnight shipping. If you paid for shipping prior to February, you paid for standard shipping and that's what you're getting, whatever name you want to call it. Chances are, if you paid for shipping after February, you also paid for standard shipping. There is no one that paid "extra" for expedited shipping prior to that.
If you want to upgrade your shipping, upgrade your shipping. If you don't, then don't, it's as simple as that. You can call the shipping anything you want, it doesn't matter to me.
Based on the USPS menu it looks like the only other 2 viable options are Priority Mail (2-3 days conus) or Standard Post (2-8 days conus). For those that may be on the fence about upgrading shipping it would be good to know exactly which service they are currently subject to in order to make an educated decision.