WGT is very tight lipped about exactly what it takes to change tiers. It's not just based on your average like a lot of new players think.
Let's just say your average is 115.00 and you're still a HACK. Reason being would be that either your DRIVING ACCURACY or GIR percentages are not high enough to change tiers. Both of these percentages are important statistics to the game that a lot of players pay no attention too until their trying to make Master.
Example: There are many Pros out there that have 64-66 averages but have not made Master due to their DRIVING ACCURACY and GIR not being high enough.
Keep playing ranked rounds. Every round you play effects your averages. The more rounds you play the more consistent your averages will be.
Best of luck!