Can't find Order ID on website is broken

I need to cancel an auto renewal subscription for Avast Internet Security (currently with about 32 days until it renews itself) and since I accidentally deleted the e-mail with my Order ID number in it, I tried to recall the number via your website service to do so.

However, I am asked for the last five digits of my credit/debit card and yet when I go to enter this information, I am told that I only need to enter the final 4 digits of my card and when I do this and press the button to start the process, I get a message that says ‘Invalid information’ and an option to go back to the previous page.

Contact avast or the payment processing company.

Turn off Auto Renewal:
https://www.avast.com/faq.php?article=AVKB24#idt_0100

You can also look at/change the auto-renewal yourself here: https://www.avast.com/find-order