Incoming/outcomig can not be reenabled after releasing full mailbox

Incoming/outcomig can not be reenabled after releasing full mailbox

Hello,
incoming/outcomig was automatic disabled due to 100% usage of email box. The user deleted some messages and now the usage is 88%. When I try to enable incoming/outcomig in the Mail administration / mail acounts, I get message "Operation permitted for paid user(s) only". The user is veronika@tmtplus.cz.
Thanks for help in advance
Viktor Terinek