Xiaomi India — Not getting proper information about my phone

Address:	Thane, Maharashtra, 421003
Website:	miui.in

I submitted my phone around 22 days ago in service centre. I was facing minor issue of jack. So they said motherboard will get changed. They said it will done by 8 to 10 days. They are still not giving me the commitment that when it will get repaired. The worst service i have ever seen in my life. I submitted my phone in teenhaath baja branch, thane, mumbai. Plz help me how should i file the complaint against them. Plz help.