Why can't I pick my set?

I paid $145.29 for this ticket the reason I can't sit way at the back cuz it hurts my ears but it known that I have paid more for my ticket so this means that you're not going to help me then

From the exit roll to the rear are FREE SEATS. When those have all been taken those left are the premium seats/choice seats. Up closer to front , more legroom , easier on & off. We haven't always charged but I believe other major airlines excluding Southwest charge for seats

You probably purchased the new basic economy ticket