When I wrote about making a phone call to request a refund, Chelsea asked exactly how that worked.
Here's what I do:
Scenario 1) The mistake is the fault of the company. A few months ago, Bart and I noticed (thanks to Mint.com) that our cell phone bill was about $10 higher than normal. A quick look back showed us that we'd paid about $32 extra over the course of three months in internet fees on our phones because any time our new phones were dropped or bounced around in a pocket or purse, they connected to the internet. I looked up all our old bills online and added up the additional fees so I knew exactly how much we'd be charged.
I called up the phone company and politely explained that our phones were connecting on their own to the internet and we were being charged connection fees that had, since December, totaled $31.17.
I asked that first our next bill be credited the exact amount extra we'd paid and that second, they change the settings on our plan so that our phones would no longer connect to the internet.
The woman looked at my account and made the necessary changes and I was off the phone in less than ten minutes. Of course, I thanked her effusively.
Scenario 2) This is the less-pleasant one where the fault is your own. The first month we were married, in the hubub of a wedding, a move, two receptions, and the beginning of a new semester, we didn't pay our credit card bill on time, which meant we got dinged with a $30 late charge. If you think I'm a penny pincher now, you should have seen me when we only made $8.50 an hour.
Bart called up the credit card company, gave them his account number, and explained that he'd had this card for X number of years and never once been late with his payment until now. He apologized profusely and asked if, this once, they would waive the late fee. And what do you know? They did.
Five minutes, thirty bucks saved. All you have to do is ask. Preferably very politely.