We are sorry but no...
If you are in an active billing period you can't change from monthly billing to yearly billing.
But you can write us that we can make your changes active in the next period.
Please notice that the next period is one year.
You have a webpacket since April 2019 and buy it monthly. In September 2019 you want to change it to yearly billing.
We are set it up in October and you will be charged for one year since October (October 2019 to October 2020).
For that please write us (firstname.lastname@example.org).