Windows :: PLS-00306 / Wrong Number Or Types Of Arguments In Call To VALIDATE_PATIENT_NEW

When My C# program executes the cmd.ExecuteNonQuery(), the following exception is thrown:

[System.Data.OracleClient.OracleException] = {"ORA-06550: line 1, column 7:
PLS-00306: wrong number or types of arguments in call to 'VALIDATE_PATIENT_NEW'
ORA-06550: line 1, column 7:
PL/SQL: Statement ignored
"}

Here is my Stored Procedure:

CREATE OR REPLACE PROCEDURE VALIDATE_PATIENT_NEW
(
P_LAST_NAME IN ogen.gen_m_patient_mast.last_name%TYPE,
P_FIRST_NAME IN ogen.gen_m_patient_mast.first_name%TYPE,
P_DOB IN OGEN.GEN_M_PATIENT_MAST.BIRTH_DATE%TYPE, -- timestamp DEFAULT NULL,
c_dbuser OUT SYS_REFCURSOR

[code]....

Here is my C#

OracleConnection conn = new OracleConnection("Data Source=SRVORDERS;User ID=OGEN;Password=xxxxxx;Unicode=True;");
try
{
OracleCommand cmd = new OracleCommand("OGEN.VALIDATE_PATIENT_NEW", conn);
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.AddWithValue("LAST_NAME", LAST_NAME);
cmd.Parameters.AddWithValue("FIRST_NAME", FIRST_NAME);

[code]....

I suspect the error is caused by the Cursor parameter.