Using two instances of a custom method results in 'call is ambiguous'
<p>I'm having trouble with compiling my code, I'm getting the following error from the compiler: </p>

<blockquote>
  <p>The call is ambiguous between the following methods or properties: 'ActionTracker.DataAccess.GetSpecialtyCode(string)' and ActionTracker.DataAccess.GetSpecialtyCode</p>
</blockquote>

<p>I'm just using my custom method again in a new method. I've used another method in exactly the same way as this and I haven't gotten any ambiguity errors. Please can someone help? I'm a n00b :D</p>

<pre><code>namespace ActionTracker
{
  using ...
   internal class DataAccess
   { 
     internal static string GetSpecialtyCode(string name)
     {
         OleDbConnection speccconn = SetUpConnection();
         speccconn.Open();
         OleDbCommand specccmd = new OleDbCommand("SELECT Specialty_Code FROM tbl_specialty WHERE Specialty_Description = @Specialty_Description", speccconn);

         specccmd.Parameters.Add("@Specialty_Description", OleDbType.VarWChar, 255).Value = name;

         string code = (string)specccmd.ExecuteScalar();
         speccconn.Close();
         return code;
     }

     internal static string AddVisitSpecialty(string trust_name, DateTime visit_date, string visit_type, List&lt;string&gt; specialties)
     {
          int visit_id = GetVisitID(trust_name, visit_date, visit_type);
          OleDbConnection visitspeccon = SetUpConnection();
          visitspeccon.Open();

          foreach (string element in specialties)
          {
            string specialty_code = new GetSpecialtyCode(element);
            OleDbCommand visitspeccmmd = new OleDbCommand("INSERT INTO tbl_visit_specialty (Visit_ID, Visit_Specialty) VALUES"
            + "(@visit_id, @visit_specialty)", visitspeccon);
            visitspeccmmd.Parameters.Add("@visit_id", OleDbType.Numeric).Value = visit_id;
            visitspeccmmd.Parameters.Add("@visit_specialty", OleDbType.VarWChar, 255).Value = specialty_code;
            visitspeccmmd.ExecuteNonQuery();

           }

           visitspeccon.Close();

           string message = "Specialty(s) added to visit";
           return message;
     }

     internal static string DeleteVisitSpecialty(int visit_id, List&lt;string&gt; specialty_list)
     {
         OleDbConnection delvscon = SetUpConnection();
         delvscon.Open();     
         List&lt;string&gt; specialty_codes = new List&lt;string&gt;();

        foreach (string element in specialty_list)
        {
            string specialty_code = GetSpecialtyCode(element);            
            OleDbCommand delvscmd = new OleDbCommand("DELETE FROM tbl_visit_specilaty WHERE Visit_ID = @visit_id AND Visit_Specialty = @visit_specialty", delvscon);
            delvscmd.Parameters.Add("@visit_id", OleDbType.Numeric).Value = visit_id;
            delvscmd.Parameters.Add("@visit_specialty", OleDbType.VarWChar, 255).Value = specialty_code;
            delvscmd.ExecuteNonQuery();
        }

         delvscon.Close();
         string message = "Specialty(s) deleted";
         return message;
      }
   }
}
</code></pre>
