Dont register online.It must be a bug.If you have an MTNL phone line already,then you will only have to pay what ever is the monthly charge for your plan that would be Around Rs.800.Registration and Insatllation is free till 20th October.If you don't have an MTNL phone line then along with the above mentioned cost,you will have to take an MTNL phone Line which will cost Rs.500 one time installation and then monthly Rs.200.And thats it