Vodafone India — repeatedly getting bills still after termination of the connection 2 months ago

Address:

Kolkata, West Bengal

On 26th aug i visited nearby vodafone store with an application and documents that i want to termiante the connection of my postpaid 3g sim. They collected the application. Then after two weeks when i called customer care, i came to know that the connection is still open and no application has been submitted. Then i visited the vodafone store once again and asked what is going on. They told it will be done, their server is down. Then i sent a mail to vodafone corporate care on 27 th of sept, and told them the whole issue, they confirmed that it will be terminated. And asked me to clear all the due bills.
After doing so, once again i got a call from vodafone on end of october, that another bill has been generatedof of an amount of around 1700. I paid that amount also, and after a long talk i was assueed that no further bill will be generated.
Then suddenly i got another mail saying bill generated for the month of nov.

May i kindly know what on earth is going on. And is this the general behaviour they do with customers using postpaid connections. Or is this any kind of professional behaviour...