Email confirmation not received for mobile contract termination

Hi, 

I cancelled my O2 mobile contract online with MeinO2  and then called the number 040 XX XXX 66 42 to cancel the contract on July 25th 2018. I was told that I will get the email as confirmation but I haven't received the confirmation email. How long it will take for confirmation email, could you please help me with this if my contract is terminated.

Thanks