New line credit

I recently transferred two mobile lines to Xfinity. I asked to take advantage of the $400 new line phone credit and trade in with the agent who completed my phone transfer over the phone. He told me I had to go to the store to do this. After he completed line transfer I went straight to the Xfinity store that day. The store said they had no idea why I was sent there and they could not help me nor honor this promotion. I then have made multiple phone calls back to Xfinity to resolve this. No one has resolved this. This seems to be an error on Xfinity side and I would like my $400 new line promotion credit honored in addition to the trade in credit. This is part of why I transferred my phone in the first place. Thank you