Xperia sp not working properly

[hema_dadlani]

I purchased Xperia sp in November last year. From starting I am facing some problems. The video quality is not good and there is so much disturbance I'm audio if I record something. The power button is not working properly. If I want to take screenshot or want to switch off my phone, it gets locked. Sometimes, it switches off automatically. I went to service centre and they are saying that we won't repair your phone under warranty.

[Thommo]

Try performing a system repair as this will often fix issues - This will factory reset your phone

Switch off your phone and unplug from Pc (Hold volume up and power for around 10 seconds)
Start PC Companion and select Support zone then Update my phone/tablet then in Blue Repair my phone/tablet and follow the onscreen instructions - When prompted connect your phone still switched off holding volume down or back button - This should start the repair or reformat process

If you are using Windows 8/8.1 or a 64bit operating system then adjust the settings for PC Companion and run in compatibility mode and chose Windows 7 or XP

If that fails then you need to either return your device to the place of purchase or contact Xperia care http://www.sonymobile.com/global-en/support/contact-us/