How do I override my touch.phase?

I'm working on my mobile game where I want to throw objects by dragging your finger on the screen and releasing them to throw. I also wish to set a constraint on the player that if they drag their finger across a specific yellow line, it will throw the object anyway.

I'm successful with the initial drag and release mechanic but I am unable to get the same results when the object the player is dragging exits a 2D trigger collider. The game still allows the player to drag the object wherever they please and this is not how my game is intended to work.

How can I override a touch.phase so that the object is thrown when exiting a trigger collider? Here's how it is set up. The throw mail function is supposed to add velocity to the object but it still won't do it despite the bool values getting changed by the trigger collider. It still thinks the player is dragging the object despite leftThrowArea changing its value.

 void DragMail()
 {
     if(Input.touchCount > 0 && GameManagerScript.instance.hasGameEnded == false) //if the player touches the screen
     {
         touch = Input.GetTouch(0);
         if (touch.phase == TouchPhase.Began) //at start of touch, has the player touched this mail object?
         {
             Ray ray = Camera.main.ScreenPointToRay(Input.GetTouch(0).position);
             RaycastHit2D hit = Physics2D.GetRayIntersection(ray, 100);
             if (hit == gameObject)
             {
                 startPos = touch.position;
                 startTime = Time.time;
                 holding = true;
             }               
         }
         if (holding == true && leftThrowArea == false && touch.phase == TouchPhase.Moved) //lets the player move this object around throuch dragging
         {
             Vector2 touchPos = Camera.main.ScreenToWorldPoint(touch.position);
             transform.position = touchPos;
         }            
         //helps determine the time being held          
         if (startTime > 0)
         tempTime = Time.time - startTime;
         if(tempTime > flickTime)
         {
             startTime = Time.time;
             startPos = Input.GetTouch(0).position;
         }
     }        
 }

 void ThrowMail()
 {
     if ((holding == true && touch.phase == TouchPhase.Ended) || (leftThrowArea == true && holding == false)) //throws the mail if the player releases the touch
     {           
         endPos = touch.position;
         swipeDistance = (endPos - startPos).magnitude;
         endTime = Time.time;
         swipeTime = endTime - startTime;
         leftThrowArea = false;
         holding = false;

         if (swipeTime <= flickTime && swipeDistance >= 50f) //throws this mail object
         {
             CalSpeed();
             MoveDir();
             rb.AddForce(new Vector2(direction.x * objectVelocity, direction.y * objectVelocity));                
             thrown = true;
             xScore = 1.5f; //resets score multiplier upon throwing the mail
             score = baseScore; //the score of this mail is reset to base value
         }
         else
         {
             Reset();
         }
     }
 }