2 months of being billed for services that I did not purchase

I have contacted AT&T about 7-8 times in the past 2 months about an astronomical bill on my account for a service that was added to my account without my permission. I continue to call, and each time I get told that I will receive an update, and yet nothing has been done to rectify this situation. No calls, no updates. Nothing but a flagrantly incorrect bill. I am incredibly dissatisfied and would like to file a formal complaint.