Your card can't be removed right now because two things are holding it on file: your Hobby subscription is still active (it renewed on October 10), and there is an open $5 invoice from that renewal that hasn't been paid. A payment method can only be removed once the subscription has fully ended and no invoices are open. Once both are true, you can remove the card yourself from your workspace billing settings.

The declined attempt on the open invoice was refused by your card's issuing bank, not blocked on our side, so your bank is the one that can tell you why the card was blocked.

But when I try to cancel my subscription, the following message appears:

"Payment required

Your invoice must be paid before you can cancel your plan."But when I try to cancel my subscription, the following message appears:

"Payment required

Your invoice must be paid before you can cancel your plan."

That message is accurate: the open $5 invoice has to be paid before the plan can be cancelled, and that requirement can't be bypassed. The invoice covers the Hobby plan fee for October 10 to November 10, and your September usage was fully covered by the plan's included credit, so $5 is the whole amount due.

Since your current card is blocked, you can add a different bank-issued credit card using the update option in your workspace billing settings, pay the open invoice, and then cancel the plan. Once the plan has ended and no invoices are open, the card can be removed.

Why am I being charged for this month if I don't intend to use the service? I would like to cancel my subscription and avoid any further charges.

The Hobby plan is billed in advance, so the $5 invoice created on October 10 is the plan fee for the October 10 to November 10 period. It was issued when the subscription renewed, since the plan was still active at that point.

Cancelling the plan is what stops further charges, but the open invoice has to be paid first before cancellation goes through. Once it is paid, you can cancel from your Workspace Billing page, and no new invoices will be created after that.