Changing wifi while connected with cable

Hi, I have 1.55. The RPi2 B has been DHCP connected to both wifi and cable to the same router. Both wifi and cable have their proper PI addresses as visible on the volumio GUI. So far so good. Now I change the wifi data for a future network (not yet active) on the GUI. Then I reboot the RPi and wait to for the fixed connection to be re-established. It does not. I tried several times with no luck.
As I only have ssh I had to restore my sd card each time.
I would like to have this working as volumio is used in a portable radio.
Thanks, Fred