There are two plans: standard and VIP.
When you go for the recurring options you will be charged automatically every month unless you cancel which you can do at any time.
The one month plan is self explanatory.
You can pay manually after it expires if you wish to.
There is an option to upgrade if you have already subscribed. The upgrade takes into account any days you may have left from your current subscription and deducts this amount from the VIP price.