Vodafone India — postpaid connection discontinued

Address:

Kolkata, West Bengal, 700016

My vodafone postpaid number is [protected] in which i was using 199 plan.
After using for 2-3 month i wanted to convert it to prepaid so i went to vodafone outlet and they offered me 50% discount on plan and requested me to continue with postpaid for which i agreed.
Next month my bill was for 199 without any discount which i paid.
Later after 1 month again i went to vodafone outlet at btm 2nd stage and requested them to convert to prepaid they too offered me 50% discount on plan but i rejected that offered and asked them to convert to prepaid.
They asked me to pay my outstanding bill which i paid on the spot and they gave me a prepaid sim.
But that prepaid sim was never activated.
After that i left bangalore due to personal reason and now i am kolkata.
I did not pay the bill because it was vodafone fault not to convert my postpaid connection to prepaid.
After 2 month my connection was disconnected.
Few days back i received a mail with threatening to clear my bill or court notice will be issued against me.
I replied to that mail with my concern but they never replied back my mail.
Again i am getting similar mail and threatening for legal action against me.
Why should i pay the bill when i asked them to convert my postpaid to prepaid twice.
They even issued me a sim but never activated that sim card.
I want my connection back because that number is linked to my bank account and other things.
I request this forum to help me out.