Vodafone — False Acquisition of pending bill after I MNP to another provider

I have ported my number from Vodafone to Airtel due to signal issues. To generate the port number the basic requirement is to clear all my dues. I paid the dues and generate the port number. As soon as i generated the port number till my number migrated to Airtel, in the span of 3 to 4 days i received 100s of calls from vodafone offering free service for 6 months along with signal booster etc.. i denied all the offers and went with airtel anyway. Now they are accusing me of a pending bill payment of 1293 Rs without any explanation.. its very basic requirement to clear all dues inorder to MNP. if i had dues MNP PORT code itself will not get generated in the first place. They are clearly taking a revenge for discontinuing their service. Now they have reported airtel about this fake bill and try to stop my service with Airtel. very cheap behaviour from Vodafone