Vodafone — excess billing for my post paid connection

Address:

Mumbai

I have ported out from my vodafone connection to another operator within my eligible billing cycle. Vodafone on purpose did not port me out on initial informed date and activated port on day 3, which was first date of next billing cycle. Since mine was postpaid connection they are now chasing me to make full payment for entire month despite only 1 day services were purposely allotted to me.
Despite of multiple mails i am not receiving any response from vodafone end however they have initiated recovery agent who are harassing me 10 times a day to close payment