Using Multiple OrganizationServices for multiple instances of Dynamics CRM Online (.Net XRM SDK)

Hello, I'm using the SDK to send data from Dynamics into our reporting system. I'm working with two instances of Dynamics CRM Online (xxx.crm.dynamics.com AND yyy.crm.dynamics.com). Right now, I instantiate the OrganizationService for xxx instance, retrieve data then send that data. When I instantiate the organization service for the second instance (yyy) and call for the data from that, I'm receiving data from the first (xxx) instance.

How do I either separate them (so I can call them both concurrently) or throw away the first instance and just use the second instance (synchronous and dirty but I'll take it)?