How do I set up the internet on my i9+++ cell phone??? (T-Mobile)?

[Ssgt's Wifey]

I called my provider (T-Mobile) and added the "T-Mobile Smartphone Unlimited Web" but when I go to "Service" then to "Common Website" and then when I try to go to "Yahoo" on my phone it says "GPRS Not Subscribed" can someone please help me???