I am not sure how things are ran here.
But usually at the 50 post mark your title automatically changes.
Then at the 100 post mark it changes.
Then at the 300 post mark it goes to "Senior Member".
But, if you want an entirely different Custom title, a more personalized one, other then
"Senior Member", "Junior Member" ect ect....
then you will have to buy it with your points.