Recently tried to upgrade Economy to Business on BOM-SIN sector. Was quote 35K miles with no taxes. The first agent was clueless and said it cannot be done because the ticket was purchased through an OTA. I disconnected and called back again. This time, I was quoted the miles after the agent kept me on hold for 15 mins. Then it took her another 30 mins to process the upgrade. The itinerary on AirIndia website shows the upgraded class but miles have not been debited from my account. It's been almost 3 weeks since the upgrade. My travel is in mid April. By when are miles debited from the account?