Apple India — iphone 7 mic issues/speaker greyed out

Address: 208005

My iphone 7 is reflecting mic issues, while calling both the parties cannot hear voice. Speaker function is greyed out & headset is not detected. "these problem arised after updating to ios 11.3"
I have read online that lot of iphone 7 and plus are showing same problems after updation due to a "bug".
Apple clearly says that phone should be repaired even if not under warranty. (Pics attached to prove that apple is aware & commits to repair) sevicer says that i can exchange my phone in 28k.
May i know why should i pay when the issue is caused due to "software bug"? Did i buy apple phone to buy back again due to technical issues caused by ios??
My phone should either be repaired or replaced asap.