static void DisplayCallInformation(Call call)
 { 
     Console.WriteLine("Call started on: " + call.TimeInstance);
     Console.WriteLine("Phone dialed: " + call.DialedPhoneNumber);
     Console.WriteLine("Call duration in seconds: " + call.Duration);
     Console.WriteLine("Press any key to continue...");
     Console.ReadKey();
     Console.Clear();
 }
        static Call FindLongestCallInHistory(List<Call> history)
        {
            Call longestCall = new Call(DateTime.Now, "", 0);

            foreach (Call call in history)
            {
                if (call.Duration > longestCall.Duration)
                {
                    longestCall = call;
                }
            }

            return longestCall;
        }
 public void DeleteCall(Call call)
 {
     CallHistory.Remove(call);
 }
 public void AddCall(Call call)
 {
     CallHistory.Add(call);
 }