//Other methods
        public static void ExecuteTests()
        {
            GSMTest instance = new GSMTest();

            for (int i = 0; i < instance.mobilePhones.Length; i++)
            {
                Console.WriteLine(instance.mobilePhones[i].ToString());
                Console.WriteLine();
            }
        }
 static void Main()
 {
     GSMTest.ExecuteTests();
     GSMTest.DisplayIphone4S();
     GSMCallHistoryTest.CallHistoryTest();
 }