This is a tough one; but, I will steer clear of opinion and make a simple statement. It applies in life in general.

If someone does not give you the answer that you like - just call again and ask again.

When you felt the resistence at the earliest stage you should have politely excused yourself, thanked and "Have a Good Day" then called again later.

The agent is correct and it is spelled out very clear in a NWA reservation. Below your flight itinerary just around your phone information and on the first page - NO UPGRADES - very pronounced on all consolidator and non-upgradeable international fares. What she may or may have not done is all subjective.

Not excusing any attitude questions - just say "Thank You" and call back again in the future if the issue is of such importance or better - develop a rapport with an Elite representative.