Savon SOAP: request returns in "Procedure expects parameter which was not supplied" in Rails

Question

Basically im trying to call a method to authenticate a player using Savon. And im getting the following error:

Procedure or function 'CORE_INCOMING_ValidateSource' expects parameter '@SourceId', which was not supplied.

Yes it IS in the methods parameter. Ive tried using it as a hash instead of a symbol to manipulate the lowercase settings and it gives me the same error.

def set_client
  @@service ||= Savon.client(wsdl: "http://services.colchian.eu/BOSS_DEMO/BOSSWebServices/IncomingIntegrationService/IncomingIntegrationService.svc?wsdl")
  end

def player_login(sourceId, sourcePassword, playerId, password, userId, workstationId, applicationId, logonSource, websiteId, partnerId, thridPartyToken)
  @response = @@service.call(:player_login) do
  message sourceId: sourceId,
          sourcePassword: sourcePassword,
          playerId: playerId,
          password: password,
          userId: userId,
          workstationId: workstationId,
          applicationId: applicationId,
          logonSource: logonSource,
          websiteId: websiteId,
          partnerId: partnerId,
          thridPartyToken: thridPartyToken
end
end

Ive used the Savon .operations method to list all the methods the server accepts. Is there a similar way to list all the parameters names for a method?