Upgrade your plan in Settings > Billing. Manage payment method and view invoices.
Go to Settings > Billing. Select a higher plan. Your new limit applies immediately. You'll be charged the prorated amount for the remainder of your billing cycle.
Harp uses Stripe for payments. Add or update your payment method in the Billing page. Invoices are available in the same place. Contact support if you need a refund or have billing questions.