At a loss to know how bags weighed and tagged as ok on one flight suddenly gain over 3kgs on the next flight. Then they want to charge $60 to upgrade your ticket. I packed and weighed very carefully to avoid any issues evan wore heavier clothing on return flight. So bag should have been lighter. Oddly when I went back for a re weigh after doing nothing to lighten the bag but made it quite clear I wasn't paying my bags were within the weight limit. Do they have a quota to meet or do they need to re calibrate their scales. Either way comes across as a scam.