Good Morning @Sambo91
The Socket you refer to belongs to Openreach so you can't move it, but there are other ways.
What does the socket look like?
Then we can help you with how to gain access to it.
so your master socket looks like A so you are using a filter?
do you have a filter in the socket you are trying to use? does the phone work in this socket?
sorry but to clarify as you should not have 2 master sockets
does the master that works in kids room have 2 sockets - 1 for phone and one for dsl/broadband?
does does downstairs have a split from face and bottom half comes off? is there a dial tone at this socket
you can also get a local telecom person to do the move far cheaper and they are probably ex openreach
You can request a socket move, I believe the cost is £130 and Openreach will come out and move it for you.
As suggested you can get an Telecoms engineer to do it far cheaper.
But whatever you do DON'T get an electrician to do it, unless they use the proper cable