If you ignore, the apartment management will send the amount you owe to collection agency and you will start receiving calls and letters from the collection agency. If you don't dispute the charge or settle with collection agency within 30 days, they will report to the credit bureaus and your credit will looks bad; not worth it.
In this scenario, go to the apartment, talk to the manager about the charges. Ask them to provide you the breakdown of charges. Then analyze it. They cannot charge you for normal wear and tear. A carpet has a life of 5 years. They can only charge the prorated amount for the damage on carpet. For example, if the carpet had cost them $1000 when they had been layed on the floor 3 years ago, you owe them only $400.
2,800 is a lot if you didn't do any physical damage to the walls or door. To my understanding, the maximum charge should look like:
1. Cleaning/ Spray - $100
2. Carpet Replacement (if damaged, for a 900 sq ft apartment) - $600
3. Ozone treatment (if you smoke) - $100
Your deposit should take care of the charges when you moved out. It is ridiculous that you owed 2.8k.
TIP: In most cases, the apartment manager is not helpful. So, you ask the number of the regional manager to your apartment manager and talk to him/her. If the regional manager is not so helpful again, then ask for the corporate manager number. Corporate doesnot want any trouble. They will waive all your charges. You might even get some portion of your deposit. Been there, done that.