U200 Lost channels without notification

I called your customer support yesterday 12/19 to discuss un-notified changes to my U-Verse channel lineup. Just a quick overview shows that I’ve lost at least three channels that I used quite often . . CHILL [#153], CLOO [#161] and LOGO [#183]. My specific concern/complaint is that I pay for the U200 service and it’s been changed without any notification, for which I’ve searched and can’t locate. The response from customer service was that these channels were switched to U300 a week or so ago and I could upgrade to U300 and get the channels back or I could switch to DISH and [they thought] I would get my channels back, but couldn’t guarantee that my total channel lineup would be the same. I’ve checked your legal notification website and found no indication that these channels will be/have been moved. I went to the ATT store and they confirmed that I do indeed have U200 service and their investigation indicated that I should be receiving the channels in question. I subscribed to U200, paid for all the services on-time and fully expect to receive the channel lineup I purchased [especially considering they haven’t been discontinued from the ATT lineup]. I don’t expect to get an ‘up sell’ just to keep watching what I purchased. I'd like to know what billing I received where I was informed about these changes or where I can go within ATT to lodge a formal complaint.