A: Your billing admin can click Settings → Account → Billing portal and then click Cancel your Upsales plan:
The cancellation has three steps. Read the cancellation notice, select one or more reasons for cancelling, then tick I understand that a cancellation is not reversible and type Cancel Upsales to confirm. The last step shows the date your Upsales account stays available until. Export your data before that date.
After the cancellation, the Billing portal shows Plan cancelled with that date.