Question

If your internet bill is $150 per month and it is

Answer 1

It seems like there is missing information. Does it mention a data cap? Often, so called "unlimited" plans have a cap where if you exceed the cap, then they charge an extra amount per gigabyte. Or they might charge per chunk of gigabytes (say 10 at a time).

Assuming there is no data cap and the cost stays the same as advertised, then the cost per month is $150 which is a flat rate.