the question is already in the topic of this message: As I have a WiFi repeater, that automatically connects to the 2.4 GHZ network, not the 5 GHZ network: Is it possible to deactivate the 2.4 GHZ network of the Sense?
Currently it's not possible to de-activate the WIFI networks in SENSE, but we'll look into providing this as a future update as we get more network configuration features developed.