Why is my internet download speed far from what I am paying for?

I have had Cox Preferred service for a number of years.  I consistently got download speeds of 30+mb and uploads of about 8 mb.  So I just upgraded to Cox Premier service and I now still get download speeds of still 30+mb and upload speeds of about 16+mb.  So Premier service is supposed to provide upload speeds of up to 10 mb and download speeds of up to 150 mb.  Why am I still getting slow download speeds and higher than expected upload speeds?