Vodafone Applegate Officer - Incorrect Billing from Vodafone

Vodafone has billed me Rs ****.** incorrectly for international roaming charges which they were unable to cater while I was travelling internationally hence there was no usage made, Vodafone informed that they would revert the charges in my outstanding but they didnt. I have already cleared my standard bill and tax amount however not paid the international roaming charges which was supposed to be amended. I have reached out to Vodafone innumerable number of times since the bill got generated , also written to Appellate however noone from Vodafone seems to be bothered. Please note that due to this attitude of Vodafone I have already ported my number to Airtel.