Yes, you can change between billing plans when using our service. You can simply do it on your profile while logged in to your Nord Account by clicking on the View Details and you will see a Change plan button. Selecting a subscription plan that you like would top up your last subscription.
However, you would need to cancel the old plan so you would not get charged automatically once the time comes.
If you have any questions or issues, do not hesitate to contact our Customer Success agents for some guidance.