Hi there @EllisBavington-Hall,
Sorry to hear about your payment issues, but happy to help and share more information about our payment process!
Essentially, Klaviyo's paid plans operate on a subscription model. You can cancel anytime, but there is not a manual payment option. Rather, your card will be charged on the same day of each month, specific to your account. If payment fails, it will be retried a couple times until it succeeds. If there is an issue with your card or there aren’t sufficient funds available in your account at the specific payment date, your account will be suspended until the payment is completed.
If you need to pay it immediately, I would reach out to our support team
Hope this helps!
-Taylor