You could connect the computer via wifi but a cable gives better performance.
How far is it from the telephone socket to the computer? Next room?
What does the computer connect to at the moment?
You could get an extension cord to run around the edge of the room to the computer. The NBN connection device (if you need one) and router and computer can then be in one place. You can do this yourself.
Otherwise, you'll need someone to relocate the socket or provide a new socket near the computer.
The wifi router should be where it will give good coverage throughout the house.
Some info on wifi: