Vodafone — Postpaid bill

I had vodafone postpaid number which is inactive from long time and in march one of your executive (Female) contacted me and said, mam please pay the bill today and i'll deactivate your sim which i did even after i was not using the sim i paid the bill and now after 2-3 months i'm getting calls and messages on my alternate number for paying the bill of 703rs. Number from which the executive contacted me is [protected] and now she's calling me again the same lady and other executives also. Why should i pay the bill when i don't have the sim.