Vodafone — Calls regarding bill payment

I have ported my Vodafone SIM to Airtel 3 months ago. I am constantly getting calls regarding payment due for a different number ([protected]) from vodafone customer care. I have no connection with that account neither have any idea whose number that is. The person's name stated by vodafone is Shirishkumar and he had given my number as an alternate contact. They claim it was linked 8 years ago. This month I got whatsapp messages from [protected] regarding due payment on my own number for 3 months (which is already ported to Airtel before that duration), also he is threatening for legal action. I confronted him on his messages and I haven't received any messages further on. To be clear I have cleared all my dues before porting and the webpage even mentions that for inactive odafone numbers. I requested customer care to unlink my number from that account of Shirishkumar and they are saying they cant. After a while when the call ended I got a message stating contakt gaming service is activated and deduted Rs 25, very strange to get that message on an no VI Sim.