No, we do not allow Windows VPS downgrade due to limitation of KVM virtualization software. In KVM based virtual machines, LVM cannot be shrinked.

For instance, if you have purchased Windows Ultimate Plan Plan with 200 GB diskspace. Later, you want to downgrade the VPS plan to Windows Starter VPS (25GB Diskspace).

Here, your VPS diskspace cannot be shrinked from 200GB to 25 GB.

The best solution is to order a new VPS at the new price and transfer your content across then cancel the old one.