Thanks all for the suggestion! I ended up calling the web desk services but the result was somewhat disappointing. After explaining my situation for hours and getting transferred to multiple agents, I was told the reservation department wasn't able to override the incorrect pricing, and they were unwilling to contact the tech department to help me figure out the root cause of the issue.
The only possible alternative was to change me over all United-operated flights, which means I had to change my destination as well because United only flies into Bogota in Colombia. It wasn't ideal, but I asked them to do so anyway just to see what happens. They did change my flights but now my reservation is in an even more messed-up state and I can't even make any changes online. I think I'll wait for a few more days before cancelling the whole trip and change my travel destinations altogether.