In Tenerife, indeed anywhere in Spain, every shop, bar, restaurant, coffee shop, has to have Hoja de Reclamación, official complaint form.
There has to be a prominent display telling you of its existence
If requested, it has to be given to fill out. If refused, they claim they do not have, do not know where it is, an offence is being committed, and should be recorded on the complaint form that it was refused.
If you have a problem, bad service, then please request the Official Complaint Form.
Fill out, or on separate sheets, you keep one copy, one goes to the establishment, two copies to government for further investigation.
Should you have any problems obtaining, inform the local tourist information office.
When Hotel Be Live Tenerife, currently a building site, but still open to clients, was asked by several different guests for the Official Complaint Form, they were given the hotel client survey form.