Round Two, Three, Four to get a replacement XG!v4-A Box.

Three weeks, a couple hours on the phone and doing live chat(s), a visit to the local Xfinity store to get a replacement for the XG1v4-A box I have that is acting up, and what do I have now; Three incorrect replacement boxes.  First I recieved a replacement XG2v2-P, then a Xi6-T, and today another Xi6-T.  Everyone I speak to on the phone, Chat with online, or even the instore employee seems to understand what I need but not one can provide me with the correct replacement.  So, over three weeks in and a couple hours trying to resolve I now have three incorrect replacements and a set top box acting up.  FOr all my trouble, a $15.00 credit which is almost laughable.  

How can so many interaactions fail, not on my part but on the part of Xfinity?