Mi Redmi - working Phone Given Back in more damaged Condition

my redmi note * , mobile phone in working conditon the only problem i was facing was it gets swtiched off after few hours and some times after few minutes.
for that i gave my mi phone to mi service store at odigi services limited , shop no.**, laxmi enclave , near gajera school,katargam- surat-******, gujarat, India.
they instead of getting solution for the problem return my phone with more damaged condition and due to their mistake my phone is not getting switch on (start) now, which was else getting start and properly working after it get switched of before i gave it to mi service center.
they are not giving any justification to my query as their reply is that out of warranty phone dont get repair in mi store.
i request to to conduct audit of the same store as i was there in store for more than one and half hour and i noticed that more than **% of the customer are not satisfied with the service of the store and unnecessary the have to pay to service cost rs.***. and due to their illiteracy they don't know the further step which can be taken against the store.
kindly do the need full.