Xiaomi India — complaint on redmi 5a

On 16th february 2018 a redmi 5a mobile was purchased from flipkart for my 65 years old father. He is a moderate user. Last week it was found that the back pannel of the handset became swell. Within 2 or 3 days it became worse. My father had been extremely worried. Yesterday the mobile get repaired by the authorised representative of mi and it took rs.1237 to replace the battery just because it crossed the 6 months warranty by some days.
This sort of incident actually broke my faith on xiaomi. This brand always says the quality of product and honest pricing. Is this an instance of quality of product???
Please dont play with the emotions and faith of the indian customers. This kind of incidents surely decay the reputation of the brand.
Yesterday i was astonished to see the other people at the service centers. They are huge in numbers and came with their phones aged just 3/5/7 months old. That was why my handset took atleast 3 hours to get replaced only the battery.
Some documents are attached in support of my complaint. Please do consider and take proper action so that no customer will have to face ill luck in future like me.
Thank you.