4G LTE Modem LB2120 automated switch over to broadband?

Hi,

Full disclosure I am not particularly technical and am after advice because I have been given two differing opinions from tech advisors..

I have the 4g modem as a back up option for small business if our NBN internet (Sydney, Australia) goes down. Current set up - NBN modem to mikrotik wireless router, ethernet connection from mikrotik to netgear 4g modem. Internet provider apparently uses DCHP to connect to NBN.

What appears to be happening is the 4g modem kicks in if NBN drops out, but then doesn't then 'hand back' to nbn when it's back online, and we are intermittently getting massive upload data going though the 4g modem. I have been advised (by IT support providing the modem)that if we connect to nbn via PPPoE it would  make a difference to the configuring the 4G modem to 'hand back' when not needed.

But our internet provider says that 4g modem should be able to 'hand back' regardless of using DCHP or PPPoE. If any techs out there can shed any light I'd be so appreciative.

It is also puzzling to me that all the excess data used by the 4g modem was uploads, and our standard upload usage is minimal when using usual nbn connections. Meantime we have disconnected the 4g modem ...

Any advice welcome, thanks.