Nexus S and t-zones / $10 dumbphone data plans

[ruprick]

Even though I am out of contract, I purchased my Nexus S unsubsidized because I HATE the idea of being tied down to one carrier for 2 years. I figured my $10 dumbphone internet plan should work perfectly for me just like it did for my Nokia N900 and Nokia N8. But I have noticed that when on EDGE speeds I get the auto-prompt to upgrade my data plan. On 3G, everything works as expected with OTA data. Why would this be and is there a workaround? Anyone else experiencing the same problem?