Not OK, but compensation awarded after complaint
Purchased a large solar panel installation, which should cover the electricity consumption in my flat and summerhouse. It turns out however that the program to be able to send the electricity from where the panels are to another is not yet available. So I bought an installation which is somewhat too large, until that program becomes available.
Also, I asked the salesperson if there would be any fees to pay to my old electricity provider, for access to the grid or any other remaining costs. He said no, but I still get a (small) bill from the old provider with exactly such costs.
The installation itself was performed by an external company and it looks good and seems all is correctly and neatly installed. All done in less than one day. The panels produce the expected amount of electricity.
I logged a complaint with Columbus and now 3 months after the installation they have provided compensation.