customer service cancelled my order with my 830$ device trade in credit with premium unlimited elite upgrade.

customer service cancelled my order with my 830$ device trade in credit with premium unlimited elite upgrade.

My Xfinity Mobile account says I'm eligible for 830$ device credit if I trade in my current iPhone with my premium unlimited elite upgrade.  I went through all the necessary steps to complete my order online. But when I go to check out it's only offering me a 400$ credit.   I contacted costumer service multiple times. At first they tell me I do qualify for the 830$ credit. I go through the entire ordering process again with them just to be told they can only give me a $400 credit. I have done this 4 different times with customer chat as well as over the phone. On November 8th I tried again. I contacted customer service through chat. she gave me the same story. Im eligible for the 830$ credit. once again we go through the entire ordering process again. Just to be told at the end it would only be $400 credit. She tells me she will speak with her supervisor to see what she can do. After some time she tells me her supervisor was able to get the $830 credit for my trade in.  She sends me the order link for me to approve. The first link crashed. she had to redo the order a second time. finally I got the order link to work. I approved the charges and the changes. The next day I received an email that the order had been cancelled. I really frustrated at this point! I have the cancelled order number and a copy of the order in my Xfinity Mobile account. Someone please help!