AT & T Phone Company Billing OVERCHARGED MONTHLY SERVICE COST FOR OVER FIVE YEARS - Refuses Refund Dallas, Texas

I have had phone and Internet service with AT&T Since 2004.  When I signed up for their USB Air Card Internet service it was for a two year contract. the contract was for unlimited data usage.

I found out in August this year after the initial two year contract was up. That they no longer offered unlimited data usage. I was never informed by mail, email, phone, or any other means about this.

The cost for the unlimited data usage was 70 plus dollars a month. After the two years contract I was continually charged the 70 plus dollars a month up until August, 2012, but was limited to a 5 Gigabit limit each month. This 5 Gigabit service cost was about $60 a month.

When I contacted AT&T and complained about the overcharge. I was told that the amount of overcharge was about $485.  I request a refund for the full amount and was told that they didn't give refunds.  Instead that the overcharge would be applied as a credit to my bill.

When it did not show up on either of my last two bills I contacted them again.  I was told that the Billing department had rejected applying the amount of credit because it was more than was allowed.

I have been unable to resolve this issue to-date with them.  If they did this to me and I didn't find out they were overcharging me for more than five years?  How many other people have they been doing the same too? How many Billions of dollars have they ripped the consumer off for?