It is unfortunately a truism that many people who have recently arrived in Spain are extremely unsure as to their rights and obligations in relation to employment.
It is all the more unfortunate therefore, that quite a number of unscrupulous employers can decide to take advantage of this lack of knowledge to the detriment of the employee.
You should therefore always get proper legal assistance before signing anything that you do not understand especially when you think that your rights are not be protected.
In the past, quite a number of naïve employees have ended up signing letters of resignation on the promise that they would receive all their corresponding right regarding unemployment, indemnity payments etc.
only to find out that no such rights arise Article 49 of the Worker's Statute enumerates a list of reasons or causes for the termination of an employment contract.
One of these is voluntary dismissal or resignation on the part of the employee.
In the case of resignation, the employee has no right whatsoever to receive compensation or a termination payment although he/she is entitled to outstanding sums owed (essentially salaries, holidays and extra payments).
It is also of note that once the employee tends his/her resignation, the employer is under no obligation to take you back on if that is your wish.
Nor would he/she be entitled to sue for annulment of the resignation due to non-agreement of the amounts paid by the company.
A suit for annulment of the resignation would only be possible under civil law if you could prove that intimidation or violence was used.
With regard to your right to seek unemployment benefit, unfortunately resignation does not give you the right to apply for this as it is not considered to be a situation of unemployment as you yourself have voluntarily brought about the termination of the contract.