[mfsch]

What can help in Switzerland (and potentially in other countries in Europe) is to complain through a consumer protection office. SRF has a TV and radio show (Kassensturz/Espresso) where they regularly solve consumer issues by threatening bad publicity.

Another option that can work is to send a bill for the owed amount and if they fail to respond start the process of debt collection (Betreibung). It’s a pain and doesn’t work well for people who actually cannot pay, but for regular businesses where you’re stuck somewhere in their bureaucracy it’s a way to force them to respond to your claims that’s a bit less involved than straight-out suing them.