Can't send text message to people that are not on AT&T/Cingular

[iBookG4user]

Ever since I've gotten the iPhone I haven't been able to send text messages to people who are not on AT&T/Cingular, but they can send text messages to me. Once I receive a text message from them then I can reply and it will get to them, but if I try to go to contacts and then text them, I get an error message saying its not a valid 10 digit number. I've tried both just their number, their number and area code, and putting one before their area code and number, all to no avail. It would be very nice to be able to text my family again who are on T-Mobile. Thanks in advance for any help!

[Roy Hobbs]

Ever since I've gotten the iPhone I haven't been able to send text messages to people who are not on AT&T/Cingular, but they can send text messages to me. Once I receive a text message from them then I can reply and it will get to them, but if I try to go to contacts and then text them, I get an error message saying its not a valid 10 digit number. I've tried both just their number, their number and area code, and putting one before their area code and number, all to no avail. It would be very nice to be able to text my family again who are on T-Mobile. Thanks in advance for any help!

Call at&t

[MyJelleo]

I've been able to send text messages to people with different carriers without a hitch.

[AJsAWiz]

Ever since I've gotten the iPhone I haven't been able to send text messages to people who are not on AT&T/Cingular, but they can send text messages to me. Once I receive a text message from them then I can reply and it will get to them, but if I try to go to contacts and then text them, I get an error message saying its not a valid 10 digit number. I've tried both just their number, their number and area code, and putting one before their area code and number, all to no avail. It would be very nice to be able to text my family again who are on T-Mobile. Thanks in advance for any help!

I agree (with others' advice). Call AT&T. I can send and receive text message to everyone. Doesn't matter which carrier they are with.

[unity]

Well an invalid number would indicate you phone numbers in the address list are wrong. With what program are you syncing with? Is it Address Book?

[iBookG4user]

Well an invalid number would indicate you phone numbers in the address list are wrong. With what program are you syncing with? Is it Address Book?

I don't sync my contact list, nor do I even use Address Book. I entered them into my iPhone manually so I know that they are the correct number, I can call them just fine. I guess I'll call AT&T tomorrow after work and see if they can fix this.