Negative transaction from mail.ru email addresses

Hi, some users with mail id’s @mail.ru are checking out with negative value and downloading for free.

sales value comes in minus i.e -$38 -$45 and customer could download the files as seen in their logs.

in user details it shows:
-$38.00 Lifetime Value

the value of the items were never free or negative.

thanks

https://wordpress.org/plugins/easy-digital-downloads/