Speaking as a tech support manager, people can get so much farther by being kind. Being firm and advocating for yourself is super important, have quotes from their website on hand to screenshot if needed to remind them of their own processes.
Best of luck seriously though. Retail is crazy this time of year and even with improved online ordering structures there's still mistakes left and right.
I used to work in customer services as well and that is so true. However, if your company has messed up big time, you have to appreciate that people will be upset and will sometimes get angry. That doesn't give them the right to berate you as though the rep personally made the problem though!
I can imagine how crazy this time of year is with people ordering like crazy. Personally, I've been back and forth with usps with a package I have (unrelated to UD) which seems to have fallen off the side of the earth. Last tracking update was two Fridays ago in the early morning - it left the town next door supposedly on the way to the local sorting depot to be delivered. Still hasn't been delivered and no tracking update
. Now it's being "investigated"!