Ixigo — cash back.

Provided with a cash back code on 2 11 2017 with expiry date as 31 12 2017. But surprisingly when i use the code system says it is an expired code. Taken up immediately with Ixigo by email and was informed that the code expired on 31.10.2017. How come expired code can be sent subsequent to the expiry date. Code was sent on 02.11.2017 with old expiry date but the communication contained a future expiry date. This came to light when i used the code.