I configured the router properly for my ISP, but i can't activate the QoS:

to configure my ISP y needed to select "custom" IPTV/VLAN configuration to fill the correct VLAN for internet. The problem is that other two VLAN's are mandatory and the router requires to fill them. I needed to put random VLAN numbers on IP-Phone VLAN ID and IPTV VLAN ID to save. 

How can enable QoS feature?