public void testCallHistory()
        {
            // add call history
            phone.AddCall(new Call("16.03.2015", "12:33", 08922315643, 264));
            phone.AddCall(new Call("16.03.2015", "22:33", 08925123643, 120));
            phone.AddCall(new Call("13.03.2015", "22:53", 08925622243, 30));
            phone.AddCall(new Call("16.03.2015", "22:33", 08956784689, 85));
            phone.AddCall(new Call("17.03.2015", "07:39", 08642234343, 522));
            // print callHistory
            foreach (var item in phone.callHistory)
            {
                Console.WriteLine(item);
                Console.WriteLine();
            }
            // prince price 37cents/1min
            Console.WriteLine("total price - " + phone.CallPrice());

            // remove longest call and print next price
            phone.RemoveCall("17.03.2015", "07:39", 08642234343);
            Console.WriteLine("total price - " + phone.CallPrice());

            // clear and print callHistory
            phone.ClearCall();
            foreach (var item in phone.callHistory)
            {
                Console.WriteLine(item);
            }
        }
        static void Main()
        {
            var firstPhone = new GSM("Gnusmas", "sS", 3, "Acho");

            // GSMTest.Test();

            firstPhone.AddCall(new Call("15.03.2015", "23:43", 0894234324, 230));
            firstPhone.AddCall(new Call("11.03.2015", "01:35", 0882356342, 120));

            // Console.WriteLine(firstPhone.CallPrice());
            // Console.WriteLine(firstPhone.callHistory[0].dialledPhoneNumber);

            GSMCallHistoryTest gsmCallHistoryTest = new GSMCallHistoryTest();

            gsmCallHistoryTest.testCallHistory();

            firstPhone.Battery = new Battery(BatteryTypeEnum.LiIon, 213, 4324);
            Console.WriteLine(firstPhone.Battery.batteryTypeEnum);
        }