Request an XG1v4 TV box

Hello Xfinity, 

I live in Washington DC and just bought a Bluetooth soundbar, I would like to connect it while watching the TV. I google it and found to request a new XG1v4 tv Box to replace my current TV box is a solution. But I went to the Arlington, VA store today, the lady there said they don't have any left in the store and asks me to do so online. I called but the agent picked up the phone told me I should go to the store instead. 

I don't know what to do. I just need to upgrade my current TV box to the XG1v4 box. Any information will be highly appreciated. 

Best, 

Jeffrey