Modem problem in Airtel broadband-not working

Hello!
I am using Airtel broadband from the last few years, and if the modem gets not working then Airtel helped to correct this one. But recently, I get the problem with the modem and for correcting this problem I contacted with the Airtel, but now they are saying that they have changed policy and now it has to be done by consumer itself through seller service centers on charge basis. I am not getting here that who will not correct the problem of this modem, this is because, they have told that for correcting the problem I have to contact whit the seller service, but this modem I have got from the Airtel only??? Who own this modem now? I don’t know, please suggest me some way if you are having the suggestion about this and also tell me what does client agreement say about it? If you have some information about this.