Unless the company welcome unfair dismissal charges against them; then under Spanish law they are required to provide you written correspondence of the facts (of the alleged infringement) prompting the dismissal and effective date of dismissal.
#If no proven facts, then it would be considered 'unfair' and likely 'NULL' if the dismissal is motivated by any of the discriminatory causes prohibited by the Constitution or Law, or if any of your fundamental rights or public liberties are breached. The consequence of a null dismissal is your immediate reinstatement, with payment of salary arrears.