Switch off 2.4ghz on extender

My car remote locking doesn't work sometimes and I believe the source of the interference is the wireless extender in my garage. It appears that when it activates on the 2.5ghz band when I am close by with a wireless device, this is creating the interference. I use the extender for wifi in my garden so not bothered about too long distances so the 5ghz band will suffice. Can I switch off the 2.4ghz band on the extender so my devices don't find it? How do I do this?