I deeply apologize for this inconvenience but the error about creating tickets was actually a bug in our system.
Our developers are working on this currently. if you would like to downgrade your plan, just go ahead and cancel your recurring subscriptions if there is an active subscription listed on your panel. Kindly go ahead and check it by going to Admin Panel > Menu > Subscriptions. If there is, then please cancel it to avoid further charges.
Then afterwards, just continue using the days you have in your premium service subscription and let it expire as it will downgrade automatically to basic plan.
I hope this answers your question.
On the other note,