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.<br>
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.<br>
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.<br>
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?'