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I am not able to send SMS from my X10 Mini Pro, the search on the sonyericsson website and i follow the instructions but under Mobile NETWORK i coundn't find SMS center to put the number that i got it from my Provider, what can i do, please help 
Many providers have a function on their website that can send the sms/data/mms settings to your phone.
You will get a notification in the top bar I think, pull it down and click the message, and you will get the correct settings installed
Also try restarting, and taking out battery and sim card.