I have shopped in Sweden or outside of the EU, Norway or Iceland
Here you can choose what is applicable to you.
I have shopped from a Swedish trader
Then you are welcome to contact the Swedish Consumer Agency's information Service, Hallå Konsument.
I have shopped from a country outside of the EU, Norway or Iceland, (not the US)
Find a consumer organisation in that country via Consumers International.
I have shopped from the US
Turn to Better Business Bureau.