This is a longshot but perhaps someone here has had the same problems.

I have an application that works fine on other GPRS networks, but on
t-mobile no
packets are ever received by the device.

We use UDP for communications, the device sends a packet and the server will
reply.  But the packet never replies. (although trying to connect to the
device via TCP doesn't work either)

The customer care machine is hard to get through (although I have trouble
tickets out there)

I am wondering if perhaps someone here can give any insight - do you need a
special apn for that? Perhaps some range of ports is blocked?  Maybe you
need to ask for somehting special in the configuration of the sim?

Thanks for any help.
Ralph