Wireless issue

Hello everyone,
How is it going?

I need some help, if possible.

I have a wireless router THOMSON TG712. I bought from a friend.
This wireless is a Voice over IP Gateway allowing (DSL).

Is there any chance I can disable DSL and activate Ethernet, so i can use this wireless because i paid for it about 80$ :s

I heard people fixed this issue but I'm not professional in IT so I'm requesting HELP if anybody knows how to do it.

Thank you kindly,

Waiting your response,