How can i get the xfinity XG1v4 4K box with DVR? I have been into store 4 times and keep getting Xi6-A

I have a 4K tv and i am trying to replace old set top box with new XG1v4 4K box with DVR.  I have been in the Xfinity store 4 times and have been sent the Xi6-A companion box 4 times.  Please advise.