WSReference.Class cannot be converted to '1-dimensional array of..

Hello everyone,

I'm getting the following error when I try to build the body section of a XML Document

            Dim WSHE As HeaderDTO = New HeaderDTO()
            Dim petitionWS As RequestCreateReceiptDTO = New RequestCreateReceiptDTO()
            petitionWS.Header = WSHE
            petitionWS.Header.Fecha = DateTime.UtcNow
            petitionWS.Header.Hora = DateTime.UtcNow.ToShortTimeString
            petitionWS.Header.Usuario = "oraclell"

            Dim bodyXML As DocumentReceiptServiceDTO = New DocumentReceiptServiceDTO ()
            bodyXML.CompanyId = "986799"

            peticionWS.DocumentReceiptServiceDTO = bodyXML

At the last line I'm getting the error:

Value of type WSReference.DocumentReceiptServiceDTO cannot be converted to '1-dimensional array of WSReference.DocumentReceiptServiceDTO'.

If you guys need anyother info, I'll be glad to add it. The header is successfully built but the body fails.

Thanks.