h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I tend to find that a mix of 'polite' and 'bull in china shop' tactics works best. If you are firm but do not lose your temper, this tends to obtain results. Like any other sort of complaining, your demeanour and presence does make a difference. This involves a verbal version of 'stand tall and make eye contact.' The best person at dealing with call centres I've ever met is my father, a teacher for nearly 30 yrs and a headteacher for the last 10. He has a voice which is polite but could quell a riot and he seems to obtain far better results than I ever manage. Mind you, even he had to resort to bull in a china shop tactics when the company responsible for the school's faulty and very loud fire alarm failed 3 times to send out an engineer at the promised time. He asked for the name and extention number of the call centre employee and promised (addressing her by name!)to hold her personally responsible if there wasn't an engineer out within the next 6hrs. It worked.
On the other side of the fence, a good friend spent seven months of her gap year working at a call centre. She got so bored she said she used to positively long for someone to ring up and shout at her. It broke the monotony and she enjoyed the challenge. I suspect she usually won most disputes !