If you bought a box, then the size of the box (or a UPC traceable to the box size) is on the receipt. I had this happen a number of times with the old MSC and always got paid. I had it happen last week with the new MSC. This is exactly what they are trying to find out. Did the clerk measure the box if it is going to Zone 5 or higher and weighs less than 5 pounds? 9of course, it has to be bigger than 12" in one dimension, and all of the approved box sizes should trigger measurement. I have also had clerks who don't measure the box correctly - interesting that it always ends up bigger, not smaller - and the price goes up even more. That is another reason why I like using the 15x12x10 box. For just over 4 lbs to Zone 5, about $16 if they don't measure it, $24.95 if they do measure it correctly.
Shopping Southeast Pennsylvania, Delaware above the canal, and South Jersey since 2008