Phone socket? You sure you're not on dial up?
Don't take the AOL person's word for it straight away. Before messing around with the phone socket, move the computer nearer to it, and try it without the extension. If you don't get an improvement you then know that wasn't the problem.
AFAIK moving of sockets etc usually should be carried out by qualified personnel, eg a sparky or someone from the phone company, if you do it yourself and something goes wrong, you might end up with a heavy bill.
Rules vary between countries/phone providers, so ask them.