Upgrade Present DVR Box for 4K UHD DVR Box XG1V4

I have been trying to upgrade my DVR box to a new box that is 4K UHD compatible for about a week now. First attempt I talked with Comcast personnel on the phone, and they shipped me an incorrect box. When I phoned them back, they confirmed the incorrect box and told me the correct box was an XG1V4.  They said they could not ship it to me unless they charged me a DVR service charge each month.  When I asked what that was, the person I was talking with said she didn't know, and I should go to my local Xfinity store to get the XG1V4 box. So, I packed up the incorrect box they sent me and took it to my local Xfinity store.  When I got to the store, I was told they didn't have an XG1V4 box and gave me a different box telling me it was 4K UHD. I took it home and hooked it up only to find that it was an older non 4K UHD box that was older than the one I was trying to upgrade. So, today I took that box back to the Xfinity store. They then told me they had no XG1V4 4K UHD boxes and cannot get any.  They told me to order one via a phone call with Xfinity.  Now I am back to square one.  Can someone at Xfinity please tell me how I can get an XG1V4 4K UHD DVR box?  Surely there is someone at Xfinity that knows how I can get this upgrade.

Thanks for any help!