Do I still have to pay Billag resp. Serafe fees with TV7?

Yes. Serafe replaced Billag on the 1st of January 2019.

The new levy for radio and television took effect on the 1st of January 2019. In principle, every private household pays an annual levy of 365 francs. It no longer matters whether radio, television, computer, tablet or mobile phone are available or in use.

https://www.serafe.ch/