Vodafone - Incorrect Billing and mental harassment

I hold a vodafone corporate plan since many years and have a standard billing plan of ***+ tax. All my bills are paid on time within the due date, However in the month of Dec ** I got a bill of ***+ tax, I called customer service enquiring about the amount difference, the telle caller informed me that since I was their valuable customer they upgraded my plan, and hence I need to pay the extra amount. I informed her that my consent was not taken to upgrade my plan hence I will not pay the extra amount and to revise my bill to my original plan. The vodafone telle caller said it wouldn't be possible as the bill has been generated, and hence I wound need to pay the amount, I asked her to close down my sim and I don't want to continue with vodafone, she tool the request on phone and I got an email staying that my number has been suspended. Now I have been receiving threatening calls informing that I have to pay the bill uptill March ** and they will not close my number. They are mentally harassing me everyday.