I linked a card to my Thingstream domain, but instead of deducting the payment, I received an invoice.

If you have set up your domain for credit card payment, we will automatically collect the amount due 8 days after the invoice is raised.  The invoice itself is provided for your reference, indicating the amount that will be collected and no further action is required on your part.

If you are not sure how you pay, please login to the Thingstream portal and go to the billing section under settings.  If you have a Pro account then you pay by credit card, if you have an Enterprise account then you need to pay by bank transfer using the account details shown on the invoice.