Hi,
I wanted you ask you guys, did you get the landline instrument or did you buy one separately with a new BSNL FTTH connection? I know there is already one thread asking about this particular question but it's quite old.
I think it requires a separate modem that supports openWRTWhy not extract setting and use in mobile phone. I think someone did it here.
Rather any spare mobile phone on flight mode with wifi on. Try client like acrobits.