Enabling Archiving for Shared Mailbox

Hi,

I have created a few shared mailbox in office365 E3 plan . I am facing a scenario where one of the shared mailbox has reached its 4 GB limit. Is it possible to enable online archiving folders for a shared mailbox in E3 plan ? Is it chargeable by Microsoft as I know that shared mailbox within 4 GB limit is free?

Appreciate comments on the above.

Thanks.