cancellation of booking without delivery

my consumer No.5221. I have registered for refill on 26.11.2011, with the dealer M/s. Prarthana Agencies, Moovarasampet, Chennai 91. I was confirmed of my booking thru' sms that my booking no. is 299837. Later I received a message on 16.12.2011 that my cash memo no.7646 is generated and the refill will be delivered shortly.And now on 26.12.2011 i am receiving a message at 7.30 pm that my booking is cancelled. On enquiring them over phone they say that door was locked. I had an aged mother at home and also a small baby. there is no chance of locking the door at all. Now on 25th my mother has expired and i am finding it difficult without a gas cylinder .Moreover this is not the first time. Last month also the same thing happened and we had to walk to the agency office for nearly 10 days before we could get it delivered. I even came to know that a delivery boy by name Sunder is repeatedly doing like this and the officials at the office are also aware. Now they want me to book a refill again. Kindly help me with the delivery of the cylinder immediately