Wireless Advocates AKA Costco Wholesale AKA Wireless Advocates at Costco Wholesale Purchased 2 Iphones on Buy One Get One offer, ended up being charged fully for both phones. Seattle Washington

On April of 2016, while looking to purchase one Iphones in Costco Wholesale in Westbury, NY, the sales person told me that they have buy one get one offer for Iphone SE and if I buy one with new line, I would get another Iphone for free.
My wife also got interested and wanted to upgrade her phone as well and eventually we agreed to get the offer.  I purchased new Iphone SE and changed my phone number to be eligible for the get another free offer.

After few months, realized that ATT has been charging me for full price for both of the new phones in monthly basis.
I went to ATT store, and they said that they had Iphone 6 on buy1 get 1 offer and not Iphone SE, and on top of that, this issue should be handled by the kiosk in Costco Wholesale where I purchased it and ATT has no involvement in this.
I went back to kiosk in Costco Wholesale and they said me to go to ATT.  After explaining that I already went to ATT, they said they will raise the complaint entry and escalate it, and asked me to followup in a month.  Since September 2016 when the first complaint was raised, I have been following up to them again and again every time being said that it is under review and to followup next month.  
Today on my followup, they said that mgmt has reviewed and found that I had signed papers on purchasing two phones and that didn't mention anything about buy one get one offer. 
I am a good customer of COSTCO and love their business practice, and based on that I didn't give much thoughts on reading those many pages of contract when buying the Iphone.

* First of all, this is definitely a fraud from Wireless Advocate on giving false information (that Iphone SE is in buy one get one when actually Iphone 6 was )to customers, and then charging them for both phones.

* Second, this is bad on Costco as well, because when we customers come to costco, we come there to get COSTCO level of quality and customer service.  However having other companies selling their products with deceit on COSTCO's name is bad for COSTCO's image as well.

THIS FRAUDULENT selling tactics needs to stop and the company should look into this issue in detail.
I am going to complain this issue on every front and every people I come across with until this is resolved.