Apple has launched free service program for these iPhones

Apple has announced a new service program for a small percentage of iPhone 12 series users. The program addresses sound issues that some iPhone 12 series models may be experiencing during calls. So if you own a iPhone 12 series phone that does not emit sound from the receiver when you make or receive calls, it may be eligible for service.
Which iPhone models are eligible for the service
The service will cover iPhone 12 and iPhone 12 Pro models. However, not all iPhone 12 and iPhone 12 Pro models will be eligible. Affected devices may include those manufactured between October 2020 and April 2021.
The service will be free of cost and will be provided by Apple or an Apple authorised service provider. However, iPhone 12 mini and iPhone 12 Pro Max will not be part of this program.
Apple notes that the repair program covers affected ‌iPhone 12‌ or 12 Pro devices for two years after the first retail sale of the phone. In case the phone is damaged that affects the ability to complete the repair, that issue will need to be resolved prior to the service. In such cases, customers may have to pay for the additional repair.
Those impacted by the issue can book an appointment at an Apple retail store or an Apple Authorised Service Provider. They can also reach out to Apple Support to arrange a mail-in repair.
Also, the program doesn’t extend the standard warranty coverage of the iPhone 12 or iPhone 12 Pro. Apple may restrict or limit repair to the original country or region of purchase.