XML Nota Fiscal Electronic Header

I'm having a problem formatting the message we sent to the web service of the sefaz to consume the NFe service.

I send this String to the web service:

var sbXml = new StringBuilder();
            sbXml.Append(@"<?xml version=""1.0"" encoding=""UTF-8""?>
             <consStatServ xmlns=""http://www.portalfiscal.inf.br/nfe"" versao=""2.00"">
             <tpAmb>2</tpAmb>
             <cUF>35</cUF>
             <xServ>STATUS</xServ>
             </consStatServ>");

I'm just getting this:

<retConsStatServ versao="3.10" xmlns="http://www.portalfiscal.inf.br/nfe"><tpAmb>2</tpAmb><verAplic>SP_NFE_PL_008f</verAplic><cStat>239</cStat><xMotivo>Rejeição: Cabeçalho - Versão do arquivo XML não suportada</xMotivo><cUF>35</cUF><dhRecbto>0001-01-01T00:00:00+00:00</dhRecbto></retConsStatServ>

Indicating the following error: Unsupported XML file version

Does anyone know what modification I have to do ?, I already checked the version is right, the Web Service accepts.