Depending on your carrier, you may be able to access some of your carrier’s services directly from iPhone. For example, you may be able to check your bill balance, call directory assistance, and view how many minutes you have left.
Choose Phone. Then scroll down and tap the button for your carrier’s services.
When you request information such as your bill balance, your carrier may provide the information in a text message. Contact your carrier to find out if there are any charges for these services.