If you have low bandwidth and the voice chat feature enabled, this can cause increased lag and connection drops.
To disable the use of the headset:

1. From Main Menu choose Multiplayer 
2. Choose Online Game
3. After it finishes connecting, the online game screen should come up. Choose Player Profile
4. Choose Player Options
5. Set the Voice Chat option to OFF.
6. Press the X button on the controller to accept the changes.

You will also need to go into the Audio Settings menu, again this is accessed through the Player Profile screen.

1. In the audio settings screen, set the Microphone Level to OFF and the Input Device to Do Not Use
2. select OK and then press X on the controller to confirm the changes.

Once voice chat has been disabled, you should notice a significant drop in lag and disconnections.