Sony India — Phone screen goes blank when makes call

Address:

New Delhi, Delhi

I bought sony z ultra last year august.this year it was not charging so the service centre gave me a refurbished set.I had to again get the screen guard put when the set was not even new.now after a month the refurbished set screen goes blank as soon as I make a call and the blank screen stays like that only and can't use the phone until the call doesn't get disconnected from the other end.my complaint is why did I have to go through so much mental trauma of going all the way to lajpat nagar and still such a reputed high end phone is refurbished and a new set not given and still people are not able to hear my voice also when I speak from this phone,