ATT Confusion

The story of a pretty red Samsung.
When we were in Europe this winter I had son Jon unlock this phone with codes found on the internet so I could use a Belgacom Pay and Go card for local calls in Belgium. I put the ATT sim card in my eyeglass case and made arrangements with ATT for what I thought was a sort of minimal fee to keep the phone number.
In May I went to Radio Shack and spent 1 1/2 hours getting the phone reactivated and returned (I thought) to the previous calling plan (500 minutes and rollover). Surprise, Surprise. They kept the calling plan that I had been given when the phone was unlocked--a minimal fee and a charge of 45 cents per minute for usage.
I did not notice until I got a note this month indicating a problem with my calling plan. Translate that to mean large charges.
So things are straightened out now. I have a new (old) calling plan and they did take off the per minute charges for the bill I will not even get until after July 25th. I told them I suppose that is better than the civil or criminal penalties they might have faced for eavesdropping on all our phone calls.
Trapped in the corporate system.