Query AVG annual subscription

Hello,  I paid £79.99 on 17 May 2021 for internet security all devices.  I received 

another email with invoice for £49.99.which is due on 21 July.2021 .  I am querying

what is the difference.  Is there a mistake - as I do not want to pay for the same

product twice.  Can you explain please?  Note I did the same last year but did not
notice…Thank you