I don't think you can simply change your purchase to permanent license. What you can do is to refund for the subscription purchase and purchase a permanent license after that.
Or, you can raise support ticket using the link below, use "ask a question" option. Include all information details. Remember to record down the ticket number for future reference if needed. Do not raise multiple ticket, that will make your ticket back to the end of the line. Send once and wait. Ticket will be answer by the order they send in.
https://stardock.atlassian.net/servicedesk/customer/portal/4/group/13
Thanks
Basj,
Stardock Community Assistant