Up until recently, I've never used (or needed/wanted to use) text messaging. I have a Cingular plan with a Sony Ericsson T300 (I think), which I got for free when I upgraded my plan to include my dad. As of now, I'm on a pay-per-text plan. Now, on to the problem. I can't send text messages at all. I can receive them just fine, but I just can't send them. Whenever I do, I get an error message from my phone telling me that it can't send the message. Keep in mind that I've never sent a text message on this phone before. My brother, who I believe is on a different plan (I can't remember whether or not he was added into our plan a little later on) is able to send and receive messages even though we have the same service center number. I called Cingular about this and they tried giving me a new service center number, but that didn't work. Next, I tried going to my local Cingular store, but they weren't able to do anything for me unless I had my dad's account info (the plan is under his name). Is there anything I can do to remedy this? My plan expires in the summer, so I may just wait it out until I get a new plan and phone. Granted, this isn't of great importance, but it would be nice to be able to text my friends back. Thanks in advance for your help.