Newegg will not let me return my Gigabyte PSU which is S/N 20333G020710
if you have a ticket open with them tell them it needs to be elevated to a higher tier support agent or manager.
showing them the discrepancy in what was stated vs what your actual serial number is should get this rolling.
if they refuse then i would be concerned that this is some bs by Gigabyte.
there should be a special Return Policy linked on the item's product page at Newegg if so.
i've heard nothing good about Gigabyte in the last year+ but possibly contacting their support and explaining the situation could get them involved in fixing your Newegg fiasco.