Welcome to FT. If you had come here earlier, we might have been able to advise you...
- Don't book codeshares if you care about managing your booking in advance
- Don't use an Online Travel Agency
Your only chance of getting a full refund on a non-refundable ticket is if there is a significant schedule change between now and departure. If you try to involve your bank now, your chargeback will be declined - you have a perfectly valid ticket to fly to Spain - and you will have no further recourse.
Hopefully you will receive your multiple seat selection fees refunded in due course. Don't try again - it won't work.
When online check-in opens 24 hours before departure, you may be able to select seats. But you may be simply assigned a seat and will be unable to change it.
Although frustrating, your situation is unlikely to be resolved. Learn the lesson to not use OTAs to book codeshares in the future.