I don't know about T637, but I've used a factory unlocked SE K700i (which
is another SE phone that T-mobile does not support officially) with my T-
mobile sim recently, and had no problems setting up all the services.

If your T637 is factory unlocked you should not have a problem. Insert your
sim and make sure phone is working. Then go to SE web site:
<http://www.sonyericsson.com/spg.jsp?cc=global&lc=en&ver=4001&template=ps1_
1_1_1&zone=ps&lm=ps1_1>

Select your phone model, country (usa), provider (t-mobile), enter your
phone number, and it will send you all necessary configuration over the
air. It took me about 5 minutes to have everything up and running on that
K700i I had for a few days. Your phone is in the list there, so it should
do it for you as well..

If you phone is not factory unlocked (e.g. is branded for some other
operator, but was sim-unlocked at some point) you should research more
carefully, because some operators lock GPRS settings and such, so that even
though you can use phone with other company's SIM for voice, it won't take
the new GPRS settings. I think SMS should be no problem in any case though.

LEM.
(remove all digits from adress for direct reply)

CaptWiggum@gmail.com wrote in news:1113243913.106829.143690
@g14g2000cwa.googlegroups.com:

T637 GPRS is working fine with T
you need configuration setting