Swapping my licence key to internet security free

AVG kindly sent me details of how to download and install internet security, but the issue is when I try to put my key into the present free one, it says "We have cancelled this because internet security is already installed"!!
Please, how can I put my licence key into the free one?

Hello, Colin,

We apologize for the inconvenience caused. Could you please share the screenshot of the AVG window that shows the message as "We have cancelled this because Internet Security is already Installed" and also the version number of AVG Protection?
You can check the version number from the system control panel. Click on the link to get the instructions to attach the screenshot of the AVG window: http://support.avg.com/SupportArticleView?urlname=How-to-create-a-screenshot

Thank you.

Colin, For your info, just in case that you are unaware, you can post the screenshot here in your topic. Click on 'Answer' & then click on the 'Image' [mountain symbol] & follow the instructions. 
AVG Guru