When you opt for postpaid the below listed situations happen:
1. Your Airtel Black invoice will mysteriously increase M2M or Y2Y.
2. If you are overseas then they will auto transfer you to a payment plan without authorisation/confirmation to international package.
3. Had enough? Want to close account now? Prepare some traveling funds to run to store and back just for that!
4. Want to investigate any of these issues, your are welcome to speak with priority desk but never ever expect them to respond to your complaint.
BTW - I ended up paying Rs. 14,000 for one month of being overseas due to unauthorised activation of international package.
Till date no response received to numerous complaints filed.
I guess that's the privilege of being an MNC. They can choose to ignore any noise unless it becomes a legal issue.