Finally, move on
Look for the learning experience. However your concern or complaint got solved (or didn't), you can congratulate yourself on having the skillfulness and patience to work through the system. Ideally, you'll be able to sum up for yourself some of what you've learned in order to avoid future problems of the same type, or at least, maybe, to address them more effectively and efficiently early on.
Apply your problem-solving skills
Next time, this all will be easier. Of course, it's possible that you may end up with new concerns or complaints down the road. Or maybe your friends here will face problems that are similar to the one that you've now figured out. Knowing what it takes to deal with whatever comes up should help you to be a good resource for others while you're here. Knowing how to handle your own issues on your own also should help you outside the university, especially after you graduate, when you end up working somewhere that has its own problem-solving pathways.
Maintain positive relationships
Be prepared to meet again. Although this is a big university, the part that you circulate in may be smaller. So chances are that you may continue to see the folks you talked to in the course of trying to address your concern or complaint. You don't want to be worrying every time you step out the door about how that will go, so it might be helpful to think ahead about the best way to react.
TIP-Thank those who helped you along the way. Although any big institution can be frustrating, most of the people in it probably are trying to do their best, just like you. And most of them don't like problems any more than you do. So, if any of them really made an effort to help you to address your concern or complaint, letting them know how you appreciate that probably would make their day-and make them more eager to help others in the future.