VLAN ID is 621 for PPPOE connection

821 is VOIP and
822 is for TR069

I understand that you are running dual ISP simultaneously. Its no problem. I know this must be stupid but just to rule out ... Are u using the same router for both ISP?

Also I240G has two different types. It has VDSL and FTTH (Fibre) types. Can u tell what type of connection is your BTU?