How to flash stock EE ROM on my Samsung Galaxy S5 SM-G900F?

Hi all,

I currently own a sim free Samsung galaxy S5 Device model: SM-G900F. I'm on contract with EE in the UK and they're currently offering WIFI calling, but only on their EE devices. Does anyone know if I can flash the stock EE ROM on my S5 SM-G900F? and if so how I'd go about finding it?

Thank's in advance.