Here we go again. With no knowledge of the player, suggestions. The only condolescence is that posters really don't understand what they were told and don't try any of this stuff seriously anyway! The first thing to check is to give your horn and mouthpiece to a really accomplished player that has a great upper register and let them see if the combination is OK. My suspicion is that the hardware is just fine. Determining what could be wrong with you is something that could take 1 to 10 lessons. Fixing what is wrong is surely a project for 3-6 months. That doesn't mean crap until you are that far, it just means that we need to stay realistic and upper register with symphonic C trumpet qualities is not a plugin that can be downloaded. I do have a stupid question however: Why the hell does someone buy a professional trumpet that they can't play reasonably in tune? I mean a Bach Chicago C is not pocket change! I ALWAYS make time for my students when they buy instruments. Mistakes like this just do not need to happen.