@Eduardopiriz
I'm not 100% sure that your next step is some kind of consumer body complaint. I think you could do more with the supplier first.
Was this an internet/online purchase? If so, most of these companies have some kind of satisfaction / money-back guarantee. If so, what are the terms, and what do you have to do to avail yourself of it?
Separately, if you're not happy with your customer support, I'd advise calling them again. I'd also suggest you send them a written complaint, itemizing each of your purchased items, what is wrong with them, and what you want done about it (replacement, money back). And documenting your interactions with their customer support, and what the outcome was (i.e. no action?).
You also have different types of complaints. Everything looks good in their photos... and, yes, sometimes it looks cheap and flimsy when it's in your living room. This is not really actionable unless they have a money-back guarantee... unless it's so flimsy that it's not fit for purpose.
Wrong item, or item that doesn't match the specifications, should be a much more straightforward discussion.
You can also look at TrustPilot, perhaps you can leave a stroppy review there? Probably won't do any good, but might make you feel better. :-)
Here's a Malaga link that might be helpful:
https://www.myguidemalaga.com/consumer-protection
If your order was with Atrapa Muebles, then you can look at their TrustPilot score... which might explain your experience. Come back, JYSK and IKEA, all is forgiven. :-) Although, actually... the TrustPilot scores for JYSK and IKEA are worse than Atrapa! (Personally, we've put JYSK + IKEA in multiple apartments and we've found them perfectly fine.)
https://ca.trustpilot.com/review/atrapamuebles.com
If it was Atrapa Muebles, they DO have a money-back guarantee, but valid for 14 days. But if you want to return something and get a refund, then you have to ask for that pretty clearly within the stated period. If you expressed more free-floating dissatisfaction... and then kinda forgot about it for more than a month... it sounds like it's gonna be hard to demand action now.
https://www.atrapamuebles.com/content/11-devoluciones
As to the missing 6 cm... size isn't everything. :-) If you're referring to a foam (rolled) mattress and the difference between stated thickness and actual thickness... I think this is very common to find some sort of shortfall, and I doubt they guarantee the official number.
