Well, you don´t really have a "case" as such. They´ll quote you some reason e.g. denied credit card or something or put you on endless hold and pass you around.

I can´t tell you how much time I spent to make AT&T drop demanding a $500 deposit on my account when I added line number 3. (Short credit history in the US due to having lived here less than two years, but being their on-time paying customer all that time) After telling them I was not interested in acting as a lender to them at 0% interest and being passed to a supervisors supervisor, threatening to leave with my $150 monthly bill they finally said ok. But it was almost not worth the time. The only way some of them might understand customer service is by just saying AMF to them and going to a competitor. (Adios Mother F**ker)

Sometimes you have to ask yourself if the view is worth the climb.