I simply submitted a letter at the exchange and asked them to activate the plan after 2 days (ie 31st October). I did not have to call on any number, nor did I have to contact anyone via email/Twitter, etc. The plan successfully changed on the 31st.
Kudos to MTNL! Pretty smooth and hassle-free experience for me.
Kudos to MTNL! Pretty smooth and hassle-free experience for me.