If your card is declined in store, for your security we don't see the reason why this happens. So, you will need to get in touch with your bank/card issuer, and they will provide more information.
If this happens at the checkout, we can try the process again, or we'll ask if you have another way to pay. If it helps, to give you time to call your bank/card issuer, we can suspend the transaction and keep your shopping in a safe place for a short time.
If your query is about your online account or shopping online, please visit our Online Groceries Help Centre.