Use JSON objects or POJOs in back end service?

I'm building a back end service for mobile clients.

The requirement is that the mobile clients will pass me a token, I'll use that token to talk to other systems (behind the company firewall) in my company, and return to the user some information.

Here's a typical scenario:

A mobile client asks for some customer data and makes a call with the customers token. I use the token against the customer database system and get back the customer details. I then return the data (removing some fields that are not relevent )to the mobile client.

All data between systems (me, mobile client, customer database) use JSon.

The question is whether I should work with JSon objects throught my code or try and use POJOs?

Right now, I only need to remove some fields from the customer database before returning to the client.

The future may require more involved transformations but I can't be sure that will happen or the nature of the transformations.

Thanks