Sony India — poor after sales service for high end device xz2

Sorry to say but I am really disappointed with your poor after sales service and communication. I have visited service centre with the issue of cracking sound in loudspeaker ref. workorder no. W[protected] dated 23 Nov 2018. Unfortunately the day after service centre handed over the handset I found the same issue with the loudspeaker and again I had to visit the service centre for the same issue. This is really very annoying to visit the service centre for a single issue and keep the device at service centre for a long period. I have urged to provide a replacement unit of the same as they said there's a hardware issue which technicians denied to accept later. They took the phone second time for observation with workorder no. W[protected] dated 11 Jan 2019. However after weeks they couldn't find any issue where I faced the issue and showed them, even they agreed with the issue earlier. I tried contacting multiple times through the channel https://support.sonymobile.com/in/contactUs/ regarding the unsatisfactory service but this could not also help. From 11 Jan 2019 that defective phone has been kept in your service centre for observation till today. I hardly got the chance to keep the phone in my hand and rest of the time it's given to the service centre in the name of observation. However will it ever be replaced or I will loose my warranty by keeping it in service centre after investing huge bucks for a phone? do you offer this kind of after sales service for a high price device? This is my last request to provide the replacement regarding the issue which caused me to suffer such troubles and inconveniences a lot.