Please help me understand the CVT gear box in our Auris 1.2

[rajivrattna]

Our Auris 1.2 T with CVT gear box has been using only D1 to D5 in the auto mode even though it has D6. I can never get it to go to D6 even at 120km per hour on highways. I thought D6 was the overdrive but it does not go there. The manual mode using paddle shifters has M1 to M7 and all can be used manually. So my questions are, why does it not go from D5 to D6 on its own, without my having to switch manual mode, to go from M5 to M6 and then go back to auto mode. But after a short while it goes back to D5 as if it hates to be in D6. The other question relates to the revs which seems to go higher as you shift from M5 to M6 and why is that. They should go down I would have thought.