Change mac address of wan interface for VMG4005-B50A

Dear all is there a way to change the mac address of an interface for zyxel products? I want to change the mac addres of wan for the VMG4005-B50A, there is no such feature in the web ui but if I export a backup file there is this part

      {        "Stats":{        },        "Enable":true,        "Alias":"",        "LowerLayers":"PTM.Link.1",        "PriorityTagging":false,        "X_ZYXEL_OrigEthWAN":false,        "X_ZYXEL_WanMacType":"Default",        "X_ZYXEL_WanMacAddr":"",        "X_ZYXEL_WanMacClientIP":""      }

I tried to provide a mac address to "X_ZYXEL_WanMacAddr" and restore the file but nothing changes, I even tried to change "X_ZYXEL_WanMacType" to "Custom" but nothing changes.. any suggestions?