Problem with function parameters

Hi :

I have installed Pg 8.08

I create this function :
CREATE OR REPLACE FUNCTION CALCULO_VALOR_LIQUIDO_HELPDESK( nTipoDesconto
SMALLINT,
nTipoComissao
SMALLINT,
nDesconto
NUMERIC,
nComissao
NUMERIC,
nTotal NUMERIC )
RETURNS NUMERIC AS $$

DECLARE
nValorDesconto NUMERIC(14,2);
nValorComissao NUMERIC(12,2);

BEGIN
nValorDesconto := 0;
nValorComissao := 0;

IF nTipoDesconto = 0 THEN
nValorDesconto := nDesconto;
ELSE
nValorDesconto := ( nTotal * nDesconto ) / 100;
END IF;

IF nTipoComissao = 0 THEN
nValorComissao := nComissao;
ELSE
nValorComissao := ( nTotal * nComissao ) / 100;
END IF;

RETURN nTotal - nValorDesconto - nValorComissao;
END;
$$ LANGUAGE plpgsql
CALLED ON NULL INPUT
SECURITY INVOKER;

When i test this function, i call the function with this parameters :

SELECT CALCULO_VALOR_LIQUIDO_HELPDESK( 0, 1, 10, 10, 1000 );

This is the error that happens:

ERROR: function calculo_valor_liquido_helpdesk(integer, integer, integer,
integer, integer) does not exist
SQL state: 42883
Hint: No function matches the given name and argument types. You may need to
add explicit type casts.

I dont now what the two first parameters are see as integer. When 0 and 1
are true smallint values.

What is happeining here?

Thanks in advance.

Alejandro Michelin Salomon.