your SIM card does not allow a connection to this network

[#1]

I have the phone rooted and unlocked, and it seems to not work with t-moblie. "no service selected network (t-mobile) unavailable". I have tried doing all the resets, but to no avail. Any suggestions?

[uliwooly-wooly]

the problem might be the SIM card

try

settings -> sony ericsson -> internet settings

[#3]

No, I have used it in another phone, plus I have tried two other people's t-mobile sim cards.  Any ideas?

[uliwooly-wooly]

this might be a dumb question but do you have a data plan?

[#5]

no, i turned that capability off of the phone (plus it is rooted). that hasn't been a problem for me in the past.

[uliwooly-wooly]

ok I thought you meant that internet wasn't working

go to settings -> wireless & network -> mobile networks -> access point names -> MENU -> Add New -> enter the apn settings -> MENU -> save

you can find the apn settings if you google them

apn settings tmobile android

[#7]

"Your SIM card does not allow a connection to this network." still popped up.

[uliwooly-wooly]

so your phone its unlocked and it doesn't work with any Tmobile's SIM cards? or just yours?

if is only yours then you need to get a new SIM card

so it could be your SIM card or I'm thinking your phone its not unlocked

[#9]

it is the r800a, has the superuser app, and fails to work with any t-mobile sim card. (how do i check for sure if it is rooted and unlocked?)

[Sam]

This may be due to network locking, have you tried any other networks SIM cards in the phone?