Thanks everyone for your comments. Things are going better this time
- Made another booking today which is valid till Nov 11th (unlike last time where it was valid for exactly 24 hours).
- The person in the call center was lot more friendly this time and gave me the exact charges to be paid (which is about rs.570 for taxes per ticket).
- Called the Air India chennai office and they actually answered this time! Verified their timings - 9:30 am to 5 pm monday to saturday. 1-2 pm lunch

Parents are planning to go in early tomorrow to complete this. Home stretch I hope!