If all else fails, threaten legal action.
So back in April I paid off one of my credit cards with part of my tax refund and canceled it because of the outrageous finance charges. I got a bill of almost $80 from them this month and called to find out what was going on. After arguing with the customer care rep for about ten minutes straight she finally explained that even though I canceled the card and closed the account they were still billing for finance charges. After the date the card was paid in full and account closed.
So I asked the lady "So what you're telling me is that even though the account is closed and paid in full, your company is still charging me a fee? That doesn't sound very legal." She quickly asked me to hold so she could "see what she could do". Not five minutes later her manager gets on the phone and informs me that my balance is now $0.00 and I should not receive another bill.
On one hand I'm relieved but on the other I wonder just how many people this company is trying to screw over?