private static void Dialling(Queue <string> numbers, Smartphone smartphone, StationaryPhone stationaryPhone) { while (numbers.Count > 0) { string number = numbers.Dequeue(); if (number.Length != 7 && number.Length != 10) { Console.WriteLine("Invalid number!"); } if (number.Length == 7) { Console.WriteLine(stationaryPhone.MakeCalls(number)); } if (number.Length == 10) { Console.WriteLine(smartphone.MakeCalls(number)); } } }