How to lodge a complaint -

I want to lodge a complaint against your attitude towards a billing dispute and talk to your superior managers. .
We were surprised to see a charge of 27+72.33= 99.33 in the bill for cycle 2/8/2017 to 3/27/2017.
1. My wife spoke at length before leaving for Canada. She was told by your agent that she does not need to buy a Canada daily pack as it is covered under our plan.
.2. She told her that she bought this plan one time before. Agent reconfirmed that she does not need it. Based on agent's confidence we did not buy the plan and went to Canada.
Please check recording for above to understand if the customer is lying.

3. On receipt of this bill, She called customer service again and asked the reason of this charge. After a lot of resistance, the agent said he/she is reversing the charge.

4. We did not see the reversal in the current bill and called today again. This time again after wasting time she was told that she will not get a reversal and that the recording AT&T can not be referred to and that neither the first agent (who allowed) nor the second (who made reversal) has left any notes.

Is this customer's fault if your agents are not trained to answer questions? or do not make notes.

We are taken aback that a large company like this will behave like this. our confidence is shaken and now after going through your community forums we realize we may not be the only one.