using System;

using System.Text;  

using System.Text.RegularExpressions;           

​

public class Program

{

    public static void Main()

    {

        string nedbankMessage = "03,14738360377,1,2,2,1195253826,CASH DEPOSIT,ATM,2000.00,C,20210721,12:20:12:00,3117049.04,3117049.04,\"myraah y,\",\"0719222280myraah y,\"";

        Console.WriteLine("Old:");

        Console.WriteLine(nedbankMessage);

        string pattern = @"([""'])(?:(?=(\\?))\2.)*?\1";

        StringBuilder sb = new StringBuilder();

        sb.Append(Regex.Replace(nedbankMessage, pattern, m => m.Value.Replace(",", ""))+"\n");

        Console.WriteLine("New:");

        Console.WriteLine(sb.ToString());

    }

}

​