WorldTour-ExamPreparation(replace whithout while loop)

using System;

namespace WorldTour
{
    class Program
    {
        static void Main(string[] args)
        {
            string initialString = Console.ReadLine();
            string command = string.Empty;
            while ((command = Console.ReadLine()) != "Travel")
            {
                string[] commandArray = command.Split(':');
                if (commandArray[0] == "Add Stop")
                {
                    int index = int.Parse(commandArray[1]);
                    string text = commandArray[2];
                    if (index >= 0 && index <= initialString.Length)
                    {
                        initialString = initialString.Insert(index, text);
                    }

                    Console.WriteLine(initialString);
                }

                else if (commandArray[0] == "Remove Stop")
                {
                    int startIndex = int.Parse(commandArray[1]);
                    int endIndex = int.Parse(commandArray[2]);
                    if ((startIndex >= 0 && startIndex <= initialString.Length-1) && (endIndex >= 0 && endIndex <= initialString.Length-1) && startIndex <= endIndex)
                    {
                        int length = endIndex - startIndex + 1;
                        initialString = initialString.Remove(startIndex, length);
                    }

                    Console.WriteLine(initialString);
                }

                else if (commandArray[0] == "Switch")
                {
                    string oldString = commandArray[1];
                    string newString = commandArray[2];
                    if (initialString.Contains(oldString) && oldString != newString)// Replace whithout while loop
                    {
                        initialString = initialString.Replace(oldString, newString);
                    }

                    Console.WriteLine(initialString);
                }
            }

            Console.WriteLine($"Ready for world tour! Planned stops: {initialString}");
        }
    }
}