File storage exceeded

File storage exceeded

Hi,

Anyone have an idea why some users have loads of file storage usage? 

Deleted and inactive users are taking all my file storage and now I cannot use the CRM as I could before. I exchanged several emails with Zoho support and also spent over an hour on the phone but they don't know where I can look. 
They suggested to look into email templates and email attachments but none of that exist for these deleted / inactive users.

I don't want to pay for extra file storage when I don't actually need it.

Any ideas?
Thanks,