By law every bar, restaurant, shop and business in Spain has to have a Complaints Book, knows as "hojas de quejas y reclamaciones" which you can ask for should you need to make a Complaint in Spain.  Its a form in triplicate.  You fill it in at the establishment's premises and you keep the green and white copy, and the business you are complaining against keeps the pink copy.  You take the white copy to your local consumer office (OMIC), together with any evidence such as receipts, invoices, photographs, copies of letters/emails and so on.  You keep the green copy for your own records.

The local consumer office will then investigate your complaint and contact the company you're complaining about.  You should hear back in a couple of months, or weeks if you're lucky.  With consumer protections in Spain being way below countries like the UK, does the complaints Book in Spain actually work?

Often the very act of asking for the complaints book kicks the business in to action.  Often they won't want the Consumer Office investigating them so they will often sort your complaint out there on the spot.  This was my experience the first time I asked for the complaints book.  It was in Carrefour and I was trying to take a toaster back after it broke after a couple of months.  At first they refused but then after asking for the complaints book, they swiftly refunded my money.

The next complaint I made was against Caja Sur.  When we took our mortgage out, we had to take out 5 years’ worth of home and life insurance with them.  We sold the house after 3 years so asked my local bank manager to get the unused 2 years’ worth of insurances refunded.  They refused so we submitted a complaint via the Caja Sur website (not technically the complaints book) and a few months later we got our money refunded.

Unfortunately our next complaint against Caja Sur was not successful.  We tried to claim back our mortgage related costs from them, after reading a blog post from Maria de Castro at Costa Luz Lawyers:

https://www.eyeonspain.com/blogs/costaluz/16981/legal-tip-1425-claim-a-refund-for-fees-imposed-on-you-by-the-bank-when-opening-your-spanish-mortgage.aspx

Again, we complained via the Caja Sur website but our claim was rejected as expected this time.  Perhaps we should have used the official complaints book!  We've had to take legal action in this instance.

So generally, I think you have a decent chance of getting a satisfactory outcome to a complaint in Spain when you use the complaints book.  So go ahead and give it a try next time.  Good luck and let me know how you get on...