You cannot change the registration (annulation or registration) of subjects for which sessions have been taught in more than 20%. See Artículo 15 of Resolución del Rectorado de la
Universidad de Granada, de 11 de julio de 2016.
To change your enrollment you must fill out a form and register it at the any register point of the University of Granada or by email at epmasteres@ugr.es. One register point can be found at Secretaría de la Escuela Internacional de Posgrado (International Postgraduate School): calle Paz 17 and another one at Secretaria de Facultad of Ciencias Economicas y Enmpresariales (first floor, near the hall).
Form can be downloaded
here
You can only alter enrollment once. However, you could alter enrollment a second time if the change is due to the resolution of the call for double master with SRH or IBS or due to the resolution of internship assignation. In particular, students admitted to the double title shall cancel the registration in the Master thesis module in the first year and register for this module during the second year.
* See more informartion here