I dont know about other states but in W.B, Docomo provide monthly sms pack for Rs54, Before 1month it was Rs42.
But, with the help of this little trick you can activate this sms pack with Rs35 only.
You must Rs35 or more in your account.
Now type this text RC35 and send it to 121
Thats it.. Your sms pack will be activated within a minute.
Maximum it takes 3 hrs to activate..
tag- docomo recharge hack