Asus India — network problem all time

Address: Kolkata, West Bengal, 700010

I had given my phone to the asus service center at 30th n they returned my phone by saying your phone is ok, n all the problems has been solved and charged 500 rupee from me... But within a day the problem rises again n i hav to face problems... Please respond to my complaint or else i hav to file a complaint against asus.. Apart from that i have used another sim also to start the tower but its getting temporary connection... I have to travel from bhubaneswar to kolkata... I hav to face many emergencies,, so please tak some corrective measure n cure my phone or else i hav to take some legal action... I have tht bill in which the problems are mentioned n r charged but the problem is still the same... I m not gettng the sim tower n always shows unavailable