How can I change the location of my router/modem?

[BigE]

It depends how they wired it up. If they put DSL on the same pair as your wall jack and you still have landline phones (and have filters on the phones) then it might work. That means the DSL is on the same pair as the phones and your wall jack is probably on that pair. If they put it on a different pair, no. There are other creative wiring options. So move the router and see if it works. If it doess't sync up, then you need to investigate which pairs are hooked up at the wall jack.