How can i differentiate the userid if same userid is available in two different OU within same domain?.

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C#

directory

Hi All,
I am using ADFS ,Active Directory and asp.net based relying party application.
In my active directory structure there are two OU (customer and CustomerSupport). I am creating a user in customer OU through C# code and using UPN field as user logon name. And Creating same UserId from backend in customerSupport OU.
Now I am using below code in my relying party application for retrieving the user from OU’s.

public static string GetADPath(string userType)
        {
            if (_logger.IsDebugEnabled)
                _logger.Debug("ADHelper:Enter GetADPath");
            // Local variables
            string adPath = string.Empty;
            try
            {
                if (userType.Equals(Constants.UserType.Customer))
                    adPath = Utility.GetConfigSetting(Constants.AppSettings.CustomersOUPath);
                else if (userType.Equals(Constants.UserType.CustomerSupport))
                    adPath = Utility.GetConfigSetting(Constants.AppSettings.CustomersSupportOUPath);
                if (_logger.IsDebugEnabled)
                    _logger.Debug("ADHelper:Exit GetADPath");
                return adPath;
            }
            catch (ApplicationException appex)
            {
                if (_logger.IsErrorEnabled)
                    _logger.Error("ADHelper:Exception occurred in GetADPath. Message: ", appex);
                throw appex;
            }
            catch (Exception ex)
            {
                if (_logger.IsErrorEnabled)
                    _logger.Error("ADHelper:Exception occurred in GetADPath. Message: ", ex);
                throw ex;
            }
        }

Now my problem is if the same user-Id and password is created on both OU’s. Then CustomerSupport OU user never get login in relying party application its throw rights error.Even I have provided all admin rights in the CustomerSupport OU user’s.
But each time my application check Customer OU’s user (normal user) and user can login other application as normal user.
When I changed the password of CustomerSupport OU user’s then it’s throw “ invalid Id password error”.And user never login in the Relying Party application.
Please any one can suggest how can I handle this situation.
Thanks in Advance.