Asus India — not solving problem and doesn't pick call

Address: Ranchi, Jharkhand, 834001

My phone (Asus zenfone 3 max) was having sound problem in speaker, they don't resolve that problem and always spend my time in updating and rebooting my phone, they have changed my imei number without informing me and they create problem in finger sensor, and after all resolving this they create another problem in speaker again.
They don't receive call and treat me like foolish guy. I am a student and i can't attend my class due this.