How to query a custom picklist from Opportunity's revenue?

Hello,

I would like to query a custom picklist from Opportunity's revenue. I am using Picklist.wsdl:
myPort.getPicklistValues(myPicklist, Revenue, "");

With this operation I have the following message: denied acces. (SBL-ODS-50085).

I have tested with another entity and it works perfectlly:
myPort.getPicklistValues(myPicklist, Opportunity, "");

So, I think the problem is in the entity name, so can I access to Opportunity's revenue¿?

I am very confusing, because in Web Services documentation I have seen:
NOTE: The Revenue child object of Opportunity is actually called Product.
I have tested with:
myPort.getPicklistValues(myPicklist, Product, "");
But it isn't exists in this entity: SBL-SBL-00000