Hi Francisco Quintero,
When you are retrieving the Files , Just Retrieve the one object instead of list,
Select your entity-> in the range select first & in the XPath constraint them by some condition or association like
[CustomerMobNumber=$CustomerParameter/CustomerMobNumber]
like this
Hi Francisco Quintero,
Have an association between your customer entity and your document entity. Whenever you are creating a Document object, associate it with the Customer entity ( Entity where you are storing customer data). This will help you to retrieve documents specific to the customer.
Going with the association would be my first choice, if not possible, you can make use of the method explained by Mohammad Saqib above. The only fallback of retrieving using an attribute is that the value might change, which will not retrieve the files properly.
Hope it helps!!