Transmission when cold does not shift until 2800 rpm

Synthetic fluid is NOT recommended for your transmission. The best advice I can give you is to go and have the transmission completely flushed, and put the correct fluid, from Toyota, into the transmission. If you keep driving it with the synthetic fluid, you are going to damage the transmission beyond repair.
Also, get your money back from Sears.

I hope this helps you out. A FixYa rating for my assistance would be greatly appreciated. Thanks for choosing FixYa for assistance.

Syntetic oil is designed for operation at lower temperatures. And it wont get too viscous at lower temperature. But any way you need to worm up the autotransmission operated car at least 20-30 minutes in winture and at least 5-10 min in summer to prevent the transmission damage.
But for you car what is recommende is to use:
Coastal/DexronIII/Mercon Automatic transmission fluid
or Castrol/ATF-4 automatic transmission fluid or 5W-30 SAE syntetic Oil, but some dealers are not recommending to use syntetic oil for automatic transmission. More info about syntetic oils is here
http://heartlandsynthetics.com/ATF/atf.htm
Only one I can assume if they messed up and put regular oil instead.
Good Luck