Ok, so basically there are a few things to check before you can move the RG
How is the connection ran inside the house from the NID (network interface devcice) located on the outsided of the house? Generally its a small gray box with At&t on it. You wont be able to open it up unless its the old style and has a screwdriver slot, but then you still may only see the telephone side.
You need to find out how the signal is being brought in to the house. It is either going to be coax or rj-11. rj-11 is ethernet cable or quad wire.
Do you have TVs on the account?
((If the signal is being brought in on coax))
Yes: Then more than likely there is a diplexer on the line, it brings in the VDSL signal from the NID (sent from ATT), back feeds from the RG (coax wall plate where originally placed) aka combined, then sends HPNA to tvs. You'd have to find where the diplexer is, trace the line to the "new" location and connect in to the combined port of the diplexer.
No: Then there should be a straight coax feed to the original wall plate that gives the RG the signal. You'd have to disconnect that in the attic or crawl space and connect to the coax line where you are wanting to move the RG.
It may be difficult to trace the lines without the tools, but trial and error would evenutally find the right line.
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((if line is brought in on rj-11 and backfed to other tvs on coax))
Then you would just have to find the splitter or barrel to connect to new location wall plate.
I'll check again if you have any other questions. Make sure when you tighten back up the splitter or diplexer, the lines are pretty snug. You dont want any hpna errors. It would cause pixelation and freezing on the TVs and possibly no DVR playback.
Good luck.