Take a look at the Aydem website:-
www.aydem.comUnder Info/Helpdesk, frequently asked questions.
"What should I do to become a subscriber to the three-phase pricing?
In order for you to become a subscriber to the three-phase pricing, you need to provide an electronic counter suitable for three-phase power consumption (approved and sealed by the Ministry of Trade) and apply with a petition to Aydem Customer Relations Center in your region and sign an agreement."
There is also a contact number - Solution Centre 44 44 186 - it's possible they may be able to tell you what meter/tariff you are on???