Technical Support told me to "Shut Up"

Hello everyone. I am not the type to resolve things in a public forum but at this point I have been directed here by an ATT employee and do not know where else to go. Without going into all the details, an ATT technical support representative told me to shut up while on the phone with him. I was fairly taken back by the statement and did not press the issue then but instead called the next day to make a complaint. So far I have spoken to three supervisors who have each told me ATT would contact me once they review the case. The first supervisor who made this promise made it on the 7th. I called to see what the status of the complaint was again on the 19th. This supervisor told me there was no record of the complaint, reinitiated it and then promised to call me by the 21st. Today, I once again spent 60 minutes on the phone with a supervisor reexplaining the issue. He told me I had two options, write a letter and mail it to ATT or post here for how to resolve the issue. Since I find it hard to believe a internet/phone provider uses mail to address issues like this, I'm hoping someone here can help me resolve this. How do I ensure this complaint is actually followed through on? The supervisor I spoke to today could not guarantee to me that the employees supervisor would receive or follow through on the complaint nor would he guarantee I would hear back from ATT.