Customer service agent promise to keep an offer now they cancel my order without explanation

I am completely disappointed with the customer service that I have received from the Xfinity mobile team, I placed an mobile order on October 9 for buy one line get one free plus $830 credit with a trade in , after placing my order I called back just to verify that everything was correct and make sure that the offers where apply since in the email received confirmation was not clear, the representative that was “helping” cancel my order and create a new order which was also cancel by another representative because they were not able to fix an error on their system so I can verify my identity, all the representative said no to worried because it my order gets cancel or there’s something wrong they will be putting a note that will give me the same offer, the situation continue and I keep calling the customer to make sure they verify my order since I have submitted all documents as mentioned on their email the customer service team keeps telling that the order would not be cancel and that everything was fine in their end that they were just waiting for the verification team, I called the verification team ask them if everything was ok because my order was submitted all over again and documentation and yet haven’t received any notification, they said once again no worries we promise everything is ok and if the order is cancel for any reason we will keep your offers, to my surprise I received an email saying your order is cancel when I called back they said the system cancel because they couldn’t verify me ? Why? Why I didn’t recived and email saying something was wrong or missing prior to cancellation when I asked to re order with the same offer the representative said they can’t because the offer expired. All the promises from previous representative were not true, they made us wait for nothing and waste our time placing the order several times, horrible service