Kamayani Express - Late आना है काम तुम्हारा लेकिन मैं फिर भी हूँ तुम्हारा दीवाना - Aman

I have my ticket booked in 12904 Golden Temple Mail from Ludhiana to Ghaziabad for today in AC 3 Tier and have an Upper Berth. Due to medical issues, I cannot go for UB. I jave checked the train chart on IRCTC and have found that a Side Lower Berth is empty till Vadodara in AC 2 Tier. So is it possible to upgrade my Tatkal ticket in AC 3 to AC 2 onboard ??? Please reply fast.

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