i had at&t rare plan now but when i do the speed test it still very low so i wanna know which plan had better internet than at&t? please answer thanks

This depends on your location and available ISP on your location.
1. ISP with highest Bandwidth 16MBs +
2. If you go with Cable (Cox, Comcast etc) the location you live makes big difference that is if you live far away from the main Hub then you might experience some fluctuations between hign and low depending on number of people using the internet at that time because cable share the same line with people on that backbone.
3. With DSL there is no sharing, you will have your own dedicated line so there is no up and down like cable, but some people says DSL is a litle slower than cable but its your choice to pick. I have used DSL for over 10 years and I dont think I will move.
4. Compare the Prices and Bandwidth between Cable and DSL, also see who gives you free Router/Modem

I'm not sure what you have over in America, but I have a D-Link from TalkTalk and it's regularly over 50mbps.