Internet Slow

I just got internet and its super down load speed 25Mbps then will jump up the 200Mbps for maybe second then right back down. Its really irritating when you pay for 200Mbps service and Never Ever get only once in a blue moon even connected though ethernet. I have restarted router and all the devices multiple times. I can't even play online with my PS4 because the speed drops and kicks me out. I have tried all the troubleshooting nothing as worked so far. Need Help and Need fixed asap.