SONY
Undone repairs for a warranty fone

I purchased a Sony Xperia phone no more then 5 months ago, the phone is freezing & stalling, rebooting without switching on completely.
i sent it in for repairs, but it was returned TWICE UNTOUCHED and NOT REPAIRED. Yet claiming that it is repaired. The only thing done to my phone was the protective screen was removed!!
i find this unacceptable, as they return my fone untouched, no repairs done, and say it is a battery problem.