Sort of ... in my experience.

A week or so ago I asked them to remove the $4.99 plan as I never use the
"T-Zones" features or site ... but I am a heavy user of the connection.  (I
use a Motorola/MS Smartphone that works slick on T-Mo!!)

But ...

The CSR told me it would take about 60 minutes for my account to be updated
... I waited, and then re-booted the phone to re-register on the network.
No WAP access at all .. zilch.  Called back and they said they were having
"issues" with the free T-Zones and did not know when it would work.  She did
offer up an additional 50 minutes of "bonus" talk time for my inconvience.
I declined the time, and asked her to re-sign up the $4.99 plan as I use the
net a lot on the phone.  (Checking corporate email, etc.)  An hour later,
T-Zones worked fine.

Hope this helps!!

Happy New Year!!

Ken