No matter how much you’re pissed off by the company, try to make an effort to be polite to the people at the checkout or call-centre or whatever you’re dealing with. They’re not paid a lot for what they do, they don’t get any say in how the company operates and it’s not their fault. Put a complaint in to the bosses, Trading Standards or whoever but don’t bully the little guys on the front line. You can let them know how frustrated you feel without taking your anger out on them. Chances are they’re not doing the job because they love the company – they probably need the (minimum) wage it pays.
Just because your day’s gone to hell in a handbasket is no reason to lash out at somebody else. And have you noticed how most people are more inclined to be helpful if you’re nice to them? Lets have a little respect for the people we deal with and – just maybe – some of that respect will come back to us, and we’ll all be that little bit better off.