Cannot get 8220 working with AT&T

[ed0807]

I tried everything: I have a BB dataplan with AT&T, I changed the TCP and uploaded the service books.
But when I try to register to BIS it won't recognize my IMEI no.
I have to send a message thru Host Routing Table, which I did several times.
AT&T can't help me further with this. I've seen on several forums that it is possible, but I can't get it done.
Any suggestions?

[californiablackberry]

The 8220 is the Pearl Flip for T-Mobile.
Is your device unlocked?

[ed0807]

I have seen that page before, but my phone is already unlocked.
It works fine with AT&T for making calls and sms. The WIFI also works.
But I only have edge instead of EDGE and I cannot register it with BIS, in order to use BB Messenger.

[CCFD647]

I have a flip using AT&T service. I have the BB DATA Package and it works fine. I had to call at&t and give them the IMEI number over the phone. The I also had to register the phone with the network via through the BB itself. Also the TCP should adjust on its own from what I was told but just in case, what did you put in the TCP and how exactly did you put it in? FYI its case sensitive. Everything is caps.