i have 600 minutes for 40 $ and I added unlimited mobile web for 10$. It was working fine for about couple of months. but now the internet has some issue.
When I open any web page on the browser, it displays the message:
Subscription upgrade required.
You current plan is not Compatible with this device. Please click here to view plan options.

Next page shows the plan options. 30 $ unlimited web. 40 $ web + messaging. (when I was writing this, I was getting web page not available for the plan options, but y'day it showed like this I believe)

The URL is shown as :
http://m.web2go.com/dsb/upgraderequired/?....

I checked the settings: I am using the access point as
epc.tmobile.com

anyone has any idea about this?

EDIT
I changed the access point to internet2.voicestream.com and I got the google web page.
Speed test with 3G:
dn: 0.95 mbps
up: 0.33 mbps