Disputes
When the work goes wrong
Start with a short written note to the firm: what is wrong, the address, and a date by which you want an answer. Photos help. Keep the quote and the invoice. A phone call alone is hard to show later.
Consumer complaints
A private person who hired a business can often take a contract complaint to Center for Klageløsning (the consumer complaints centre) via naevneneshus.dk. There is a process and, in many cases, a fee. Read the current steps on that site. Nærfag is not a party to the contract and cannot file the complaint for you.
If the contract says the job is under AB 18, the dispute route may be the one named in those conditions, not the consumer board. Look at the contract before you choose a forum.
Safety faults
A dangerous electrical or gas installation is also a case for Sikkerhedsstyrelsen, separate from a money dispute. A rented home with a defect the landlord will not repair goes to the huslejenævn in the municipality. That path is described on rental repairs.