Vodafone India — Cheated by vodafone

I am Radhakrishna from bangalore . i have been using a vodafone number ([protected]) from April 2015. i had opted for 499 tariff plan, but every month my plan is changing without my request to change the plan, regarding this i have contacted customer care many times but they are replying saying that i have placed a request to change the plan, i have asked them to produce the proof that i have place a request to change, even i have mailed regarding this issues 3 times to the vodafone care. every time i get a response saying will get back to you, continuously i am facing this problem with vodafone service. now this month i have received a bill of 3999. i have decided to file a complaint regarding the same .