I use to be able to access the internet with my T-Zones subsciption with my Dash, but they cut out that service a few days ago. I called T-Mobile and they said that some people can access it but it's only a matter of time before that "bonus" runs out. They said I'd need to pay the $29.99 full internet subscription to access it again.
Then, I remembered my old Motorola MP200 and Audiovox SMT5600 settings and tried it. I use the settings discussed here (from the guy from Colorado): http://www.mobilegadgetnews.com/index.php?showtopic=4554
It partly worked on my Dash. So, I can access it again. However, I don't know how long this will last. When I access the internet with Wi-fi, I need to toggle the internet settings to "Automatically detect settings". When I use WAP, I disable that setting. It's kind of an inconvenience, but it's better than nothing.
Bottom line: if your's is still working, don't mess with it. You can try this only when your "subscription" runs out. If you can afford the full internet package, go for it.