Since the APN settings are carrier specific you need to get back to your carrier for what these settings are.

Let me share my story anyway. I had Sprint and Virgin Mobile and suffered the issue you noted. Data would bow out for days and could barely make a call or text. Turns out Sprint had decommissioned a tower in my area and that was that. I had to move to another carrier. A few phones later and a little trip to learn more about that carrier's APN settings and it's all better.