Fibre Router for ADSL connection?

[#1]

Hi
I moved house a month ago to a none fibre area and had to go back to ADSL, I was told when I called to arrange the home move that I did not need to be sent a new router as I could continue to use the fibre router for the normal connection.
I cannot get the fibre router to connect to the internet so I managed to find my old TG858 V8 router from the last time I had ADSL which does work but I keep having problems as certain devices lose the internet connection randomly (whilst others stay connected) and sometimes I have to restart the router itself.
Should I be able to use my fibre router instead as I was originally informed?

[#2]

If it's a 582n, you can install the 10.2.5.2 firmware, then use its web interface to re-configure it for ADSL use.

[#3]

Thanks very much it was in fact the 582n and I have upgraded to the relevant firmware and got it working for ADSL.
Works great now.
Thanks Again!