IRCTC/online Ticket Booking — allotment of lower birth to senior citizen as a rule if available

Address:	Jabalpur, Madhya Pradesh
Website:	[email protected]

Sir, i have booked two ac iii tickets online on 13/08/2017 from jabalpur to mumbai (Cstm) by
Mumbai garibrath no. 12187 for 11th dec. 2017. Sir at the time of booking the status of available births were 646 births. I opted for two lower births but after payment upper births were allotted to me (61 years) and my wife (56 years) which is very inconvenient for me being a senior citizen & diabetic. Sir when nearly all births are available then why i was allotted upper birth?
So kindly look into my matter and please allot me and my wife lower birth as lower births are still available. Pnr no.[protected]. Date of booking 13 aug. 2017. Date of journey 11 dec.2017.
With regards,
A k bhowmick