I generally use the rule of thumb of using who when referring to a person and that when referring to an object. Example:

Jim is someone who makes me smile.
I was nearly knocked out by the ball that hit me.

But what about when we're talking about an organisation?

I am forever indebted to the charities who helped me.
I am forever indebted to the charities that helped me.

The former seems somewhat warmer, if that makes sense, although the latter feels more correct. What should I use? And how about this:

I'm really happy with the insurance company who helped me with my claim.
I can't stand them, they're the insurance company that ripped me off.

To me the former evokes a team of helpful people while the latter evokes a cold heartless corporate entity. Is this just a matter of style and so should go with my instincts, or should I aim for what is 'correct?'