Vodafone India — regarding payment notification

Address:

Navsari, Gujarat, 396450

Sir i ws a satisfied customer of vodafone bt due to costly tarriff i port my number to airtel & now the vodafone is regularly forcing me to pay pending bill.
I don't understand that if i won't pay ur bill thn vodafone won't let me port my number to airtel.
After the bill payment i submitted the requested to port out & within 3-4 days my number ws ported to airtel thn i dnt understand how do i hve to pay 868 rs.
They are forcing me & threatening me to pag bill.