Consumer Redressal

Dear Sir/Madam, I had purchased sony perimium mobile xperia zl also my friend purchased the same,we had an issue with camera having black dots,my friend submitted phone one day later to me he recevied his swapped phone and i am still waiting each time i caall i get an answer that invoice is not generated ,if i have dposited first then why invive is not generated and they say we ahave send mail to head office but still i am not getting the answer and my phone , Kindly help me Regards, Vishal