Forced migration of plan- No reply from Nodal officer


Hello EveryoneTo cut the long story short I have Explorer 1099 Plan- 384 Kbps Day speed and 1 Mbps night speed. But recently the plan was changed and the speed now is 512 Kbps.The same thing happend 3-4 months before. At that time I complained to customer care and after about a week the changed it back to the old plan. But when it has happened now they are saying it is not possible. I said that I would cancel the connection in that case and the retention department talked about some plans but said they cant change it back to the old plan.Though I am fed up of Airtel doing the same thing time and again currently no other plan suits best. So I thought of trying my luck and complaining to Nodal officer about the issue. But there have been many days since I wrote the email but I havent got either the reply or acknowledgement of the mail. In this case what can be done and how to find out if the mail has been received? Should I contact appellate authority? Also If I try again saying I would cancel the connection they "might" offer the earlier plan but the issue is I wont ask them to disconnect until I get a secondary connection say bsnl as backup. So how do I dummy threaten them to find out if they would provide the earlier plan? :DRegards