I wouldn't to this context switch here. It's very tricky. It took me several minutes to understand that this `context` object belongs to the outer class and realize that it works. I think it would be better to make the context switch in the `receive` partial function of outer class. 

On the other hand, I wouldn't consider this class as an actor since there is no `ActorRef` pointing to it. It's a collaboration object of an actor, or a delegate. But not an actor. I would rename it as `Delegate`  or `Behaviors` (the `SellerExchange` prefix is redundant since it's a private class not used outside this file).