If you accently hit the print button twice you should be charged for one.
if you l need to cancel one of the labels go to selling manager than wait 21 days to get your fees refunded.
if you reprint a label you should not be charged. make sure the postage cost is correct before printing
500 g ebay bag $7.15
500g your bag or a 3 kilo bag turned inside out $7.45
3 kilo bag $11.70
best of luck
Anthony
