Terrible - never use GLS again!
I was waiting at home, and after 4 hours I received an email telling me that I was not at home. No phone call or call from the main door - the courier apparently just skipped my address. GLS has no customer service in Spain to call free of charge. No response from the feedback form either.
Later that day they sent me an email telling me that the package is delivered to the nearby shop. I checked with the shop - they say it's a usual misinformaiton from GLS - the package actually arrived to the shop 4 days later.