Lava Mobiles — software issue Is' system ui stopped'

Address:

jadcherla, Mahbubnagar, Andhra Pradesh, 509001

After two weeks using z62 i face some software issues like system ui stopped. Then i went to service center give it to technician, he examine and said this problem is not done here, so i return it to factory... This is done one week before till no response from that service center.. And lava care so what i do now?
Service center number is [protected], mahbubnagar, telangana.