When "contact corporate" isn't enough, how do you respond?

I've been working here about a month and a half, and I sometimes get customer complaints I can't do anything about. Turn the music down? Cool! Turn the thermostat up? Sorry. Get a splash stick? No problem! Stop your lid from leaking... Eh.

I'm not sure why people seem to think the near-minimum-wage barista at the register can do anything about some of their problems. When I say I can't do much more and suggest sending an email to corporate, half the time I get chewed out for being lazy or inattentive. It doesn't bother me much when it happens because I know I've basically done all I can, but still...

When someone asks you to do something beyond your control, how do you respond?