cheapest std calls between two numbers.

HiI am living in Delhi and my daughter is going to Banglore for her college.we need a cheapest possible plan to stay in touch.Is there anything like student plan or a plan which gives very cheap\free callsbetween two perticular numbers?I am having Reliance landline+mobile.MTNL landline.I am open to getting a third new connection from any other provider if it works out cheaper.please help.