Calculated shipping first class WRONG

[thriftybeeboutique]

Hello so I’ve been having some issues wondering if this has happened to anyone else and if there’s a solution so many of my items 10 Oz and under are charging the buyer anywhere between 1.90 and 2.00 for shipping we all know that it is more than that to ship a 10 Oz item. I ship all my items in a 13x10x5 poly mailer I included that in the  dimensions  Area of listings. Has this been happening to anyone and if so please are there any solutions? I have 800 items listed if I lose 3.00 each on 15.00 items it’s greatly eating into my margins. Please help 

[nobody*s_perfect]

Check the drop-down menu for "Package type." If that is set to "Large envelope" then  that's what your buyer will be charged for even if you select "First Class Package' in the other drop-down menu (for service).

[charity_scents]

Are you using the quick/simple listing form versus the advanced listing form? I've seen similar complaints by those using the quick form.  I've always used the advanced form and never had an issue with shipping charges being incorrect. 

[myangelandmyprincess]

eBay is charging your buyers the first class flat option and not the first class package.   You need to have first class package selected AND under package type have package selected not letter