Vodafone — incorrectly blaming for not paying bill

Address:	Gurgaon, Haryana, 122001
Website:	www.vodafone.in

Vodafone is harassing me for not paying the bill for Rs 408. I have paid the bill via freecharge (Screenshots Attached). Not I have ported my no. to Airtel. At the time of port, they said all the dues are settled and allow the port to Airtel. But after few days they started abusing, sending hundred email that I have not cleared the dues. But attached screenshot says that I have paid all the dues.

Now today I have received some sort of warning email that they will sue me if I won't pay the bill again, but Why should I pay again when I have already paid the bill?

Please help.