I am about 6 weeks out from going to Europe with my daughter using my United Miles on partner flights (LH and AC). I booked one set of tickets and when a better schedule opened, rebooked the out-going flights a day earlier (and paid the fees/taxes that incurred about 3 weeks ago). I have seen the schedule in my UA account several times and the itinerary looks exactly as it should. Tonight I decided to try once again to get our seats assigned on LH as I couldn't do it the day I booked. The website said I had a bogus confirmation code. I called UA, they verified it was fine and gave me my ticket number and said to call LH. I called them, and they said that my ticket didn't exist, but they could see my old flight (the one I changed from) and to call UA back to rebook and reissue my ticket. By now, I was really having a good time, and called again. After an hour of being put on and off of hold, the outcome was I have to call back tomorrow when LH is open UA says my "account has been noted". Imagine if we just showed up for our flights and we didn't really have a ticket to go on our vacation!! It is bad enough that using UA miles on partners, (in economy) means we can't get econ Plus or bulkhead seats etc. (Since I matched to UA Gold this year, I still might pay another change fee if UA metal flights open up so I can use that benefit, but June is a hard month to find flights without long connections). You veterans out there no doubt know all this, but maybe my story will help someone avoid a big problem with their flights.