Yes, you can upgrade and downgrade plans.
Account upgrades are effective immediately. When you check out, you will be shown the prorated amount due. This is based on the usage of your current plan.
Account downgrades will come into effect with your next contract renewal.
To upgrade or downgrade your account, go to the plans & pricing overview in your account.
Alternatively, you can upgrade or downgrade in the billing section of your account under Payment Details.
Note that you may need to archive/pause Dynamic QR Codes before downgrading.