Returning from red zone

Hello Expats, has any of you already returned from a red zone since the new testing regulations are in force? How does this work practically? On the info page it says:

"As from Saturday 2 January 2021, passengers will receive a text message upon their return with which they can register at a test centre."

I have not received this text message yet, although I have filled in the PLF. I have made an appointment for a test at my commune for the day after my return though, because it was impossible to get an appointment for tomorrow (Sunday). But can I use this QR code at the testing center in Auderghem. And do I have to pay for the two tests? The info page is silent on that part...