Demon Internet

I\'ve been a customer of Demon for over 10 years, they used to be great. Last week I called their \'customer service\' to complain when they overcharged me (for the 2nd time), they denied they had taken one of the payments, and demanded I fax or mail them \'proof\', in this case a screenshot of my online banking. Their call centre staff had no authority to let me email this, nor would they put me through to a supervisor who might have some flexibility. This is just jumping through hoops as far as I can see and so I threatened to cancel, which I also have to do by snail mail - what year is this anyway, 1990?