hiIn my case there is problem when calls are made from landline to other bsnl mobile numbers. Calls are getting picked up but no voice but bsnl mobile to landline works fine. No problem for other networks as of now. Never tried landline to other landline. We also use Panasonic cordless phone for this connection.
same problem with me but i found better solution.
go to your router and in VOIP advance settings. check where is heart bit mentioed. change the value from 0 to 60
thats it.
thanks