Send credentials in SOAP header - authentication

Question

I'm trying to develop a small program in Delphi xe10.3 to get data from a web service using SOAP.
The WSDL is https://www1.gsis.gr/wsaade/RgWsPublic2/RgWsPublic2?WSDL.
I did import it into Delphi.
The problem I’m facing is that I couldn’t find a working way to pass the credentials (basic authentication) into request header even I did use some methods I found on the web. The service responds that there are not credentials into request.
I want to mention that this is my first try to use SOAP technology and I have been confused. It will be appreciated if someone could help me to resolve this issue.
The code is :
procedure TForm1.EchoClick(Sender: TObject);
var Service : RgWsPublic2Service_Interface;
httpRio : THTTPRIO;
inpr : rg_ws_public2_input_rtType2;
ddate : TXSDate;
ReturnInfo : Result;
AskedInfo : rg_ws_public2_basic_rtType2;
ErrorStr : string;
begin
httpRio := THTTPRIO.Create(nil);
ReturnInfo := Result.Create;
ddate := TXSdate.Create;
ddate.AsDate := date;
inpr := rg_ws_public2_input_rtType2.Create;
inpr.afm_called_by := ed_myAfm.Text;
inpr.afm_called_for := ed_ClientAfm.Text;
inpr.as_on_date := ddate;
httpRio.HTTPWebNode.UserName := Ed_usname.Text;
httpRio.HTTPWebNode.Password := Ed_pass.Text;
Service := GetRgWsPublic2Service_Interface(true,'',httpRio);
ReturnInfo := Service.rgWsPublic2AfmMethod(inpr);
ErrorStr := ReturnInfo.rg_ws_public2_result_rtType.error_rec.error_code+' / '+
ReturnInfo.rg_ws_public2_result_rtType.error_rec.error_descr;
if ErrorStr <> '' then
begin
memo1.Lines.Add('Error!!!!');
memo1.Lines.Add(ErrorStr);
end
else
begin
memo1.Lines.Text := ReturnInfo.rg_ws_public2_result_rtType.ToString;
AskedInfo := ReturnInfo.rg_ws_public2_result_rtType.basic_rec;
EdEnterpriceName.Text := AskedInfo.onomasia;
mm_DoyInfo.Text := AskedInfo.doy+' / '+AskedInfo.doy_descr;
end;
ReturnInfo.Destroy;
ddate.Destroy;
end;