^^ have you tried rebooting your modem? Unplug it's power cord. Wait for a 5 minutes for internals of modem to cool. Then put it back on.
This idiotic trick has worked before. If it still doesn't work and you are sure that you have not changed any modem settings, then leave a complaint by dialling 198 from any MTNL phone.
This idiotic trick has worked before. If it still doesn't work and you are sure that you have not changed any modem settings, then leave a complaint by dialling 198 from any MTNL phone.