type command

ifconfig "eth0 or wlan0" down
ifconfig "eth0 or wlan0" hw ether 00:11:22:33:44:55
ifconfig "eth0 or wlan0" up

Remember custom mac id is always saved in the memory it's not permenant, if you restart system it's goes back to default.
And if doesn't then problem has occured.

macchanger --help
