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It's not possible to calibrate the touch screen. If you experience problem with the touch screen I suggest that you try to repair the phone software using PC Companion:
http://www.sonymobile.com/update
In PC Companion, press start on Support Zone > Start on Update the phone/tablet software > Press the blue link that says "Repair phone/tablet".
Before repairing the software in your device you may want to backup your information first. Check out this topic for more information on how to:
http://talk.sonymobile.com/t5/FAQ/Backup-amp-Transfer/m-p/407253#U407253
If the problem still persists, I suggest that you have your phone examined by a service center. Please contact your local Xperia support team for more information:
http://www.sonymobile.com/global-en/support/contact-us/
