In History, a trip you or the driver cancelled will show as Cancelled and you will not be charged the fare.
Tap , and History in your Grab app, and if it shows Cancelled, no fare charges will be made.
If the trip doesn't show as Cancelled, you can check with family, friends or coworkers who may have access to your Grab account to see if they took the trip. For GrabHitch, you will not be charged If your trip In History > GrabHitch, is reflected as Expired or Cancelled.
Let us know, after checking if the trip History shows as Cancelled, if you still believe you were charged for a trip that you did not take.