I submitted a ticket but Tech support says this is my problem to resolve.

This seems to be the answer I get to most of my problems lately. I think I'm on a list
I'm not sure what I can do when the rate returned to me is the wrong rate - so if anyone has any ideas - Please let me know.
If anyone is willing - could you test the exact setup I have outlined above and see if you get the same results on your shopping cart as well?
This would be USPS international - Global Priority Flat Rate Envelope (large)
My understanding from USPS is that a Global Priority Large Envelope is a flat rate of $12 and can hold up to 4 pounds.
I would like to verify that the wrong rate comes up for other shopping carts other than mine. So if you could test it for me I would really appreciate it.
I feel the wrong information is being sent to USPS from 3DCart or that I have something set up wrong in my Shipping Method.
I tested the shipping method on a test order to Great Britain - weighing about 1 -2 ounces. My method is set up with a max weight of 4 pounds - so the weight can't be the problem.
Thank you for any help you can provide.