Deceptive Sales Practice

I am trying to contact someone at the AT&T corporate office to file a formal complaint regarding the sales tactics and customer service I have experienced with AT&T. I have searched online for an email address and haven't found anything, so I am hoping that someone on here can help me direct me on how to file a complaint with AT&T. 

I recently switched my phone number to AT&T after years with Verizon because I was told the family share plan under AT&T would be cheaper than having my own line with Verizon. I joined another person's AT&T account and added my own line under her account about 30 days ago. My situation has changed and I need to transfer my line to my own account immediately. I was told I cannot do this because I purchased my phone under AT&T's Next plan. When the sales associate, Jennifer, sold me the phone she explained that signing up under the Next plan would be like leasing the phone and I wouldn't be under a contract or have to pay any early termination fees and I would be able to upgrade whenever I wanted to. This seemed to make more sense than buying the phone for a 2 year contract, as I was told I could upgrade to the new iPhone 6 in the fall without any penalties or termination fees. So I signed up for the Next plan. However, this is not the case. I am now locked into this contract for the next 18 months and cannot switch my line to my own name unless I pay the full retail price for the phone, which is $750! I asked the sales reps in the store and through your customer service line to please make an exception and either allow me to transfer my existing contract with the Next payment agreement to my own line and I could stay with AT&T or allow me to purhase the phone for the promotional price as I just signed up for this account less than a month ago. However, I was told there are absolutely no exceptions and I must the $750 if I want to have my own account. This is incredibly unfair as had I known that by purchasing through the Next plan I would be locked into an 18 month contract and would have to pay the full retail price should I need to change my account I would have purchased the phone outright with a 2 year contract and paid the early termination fee for ending my contract before the 2 years was up- which is considerably less than the retail price for the phone. 

The sales tactics to get me into this contract were incredibly misleading and the customer service I have been met with since then is subpar to say the least. I had Verizon for years and never was met with the kind of poor customer service as I have experienced with AT&T in the short time I have been with them. I want to transfer my line to my own name. If I am still staying with AT&T it doesn't make any sense as to why I couldn't simply transfer over my exisiting Next Contract- AT&T is still getting my money! So now, instead of AT&T gaining a customer who would be spending approximately $150 for the next 2 years, which is $3,600- because of your deceptive policies and horrible customer service, I will be leaving AT&T paying out the outrageous retail price, and taking my money elsewhere. In addition, I will make sure to share my awful experience with AT&T with every person I encounter, including those on social media so that the public is aware of how deceptive and misleading AT&T really is. I understand that policies are in place, however had I been told the the truth when I bought the phone I would never have signed up for the Next plan knowing it is in fact a contract that forces you pay full retail price for the phone should changes occur before your contract is up. Shame on AT&T. And what's worse, is I doubt any AT&T representative will actually care or respond to my plight- no matter, the public will care to know what kind of company this really is.