I have booked an apartment in Marbella and agreed with booking.com/the owner of the apartment that we could pay on the day of arrival (this was an option that could be selected at the time of the booking). I have just noticed that the owner/booking.com have taken the full amount off my card with 3 months still to go until I arrive - surely this is a breach of the agreement that we had. Is there anything I can do?
I don't think you should worry, sometimes they do. If you cancel, the amount will be refunded (if it was a free cancellation booking, in full or in part, depending on what booking you made). But in the booking.com website they state that the amount may be withdrawn anytime in full. If you have issues you can always report them to the booking.com website.
In the booking details page, they show you the expected payment schedule as well.
If you have a problem with a debit or credit card transaction that you haven’t been able to resolve direct with the retailer you can contact the card issuer to query the transaction. Some types of transaction will show as ‘pending’ on your credit card, this happens when a ‘holding’ transaction called a ‘pre-authorisation’ is applied - this is common in petrol stations or hotels, when you receive the goods or services before the final payment is requested. The pending transaction should disappear once the final transaction is processed. Pending transactions affect your available credit immediately, and once the processing is complete the transaction will show on your account and your current balance will reflect this. You are not charged interest on any purchases until the processing is complete and they are no longer pending.