You may have various options available to you, but it is vital that you understand what those options are before starting any formal procedures with your Spanish Bank.
Banks in Spain often think in a different way and therefore it is important that you understand what their priorities are before speaking to them.
For more information https://www.judicaregroup.com/site/country/lawyers-in-spain/mortgage-problems-in-spain/dealing-with-spanish-mortgage-debt/