Frustrated with slowed internet - paying for gigabit, getting ~150-180 mbps for downloads

Have had multiple service calls the past two days.  Did a modem swap and had someone check the line outside the house.  Have done multiple re-sets, but nothing has fixed the issue.  Was at 900 mbps a couple fo weeks ago.  Frustrated beyond belief.  Also am having issues with X1 video / audio sync issues (multiple box / system re-sets and nothing has fixed).  Help!