Apple I Phone 12 Pro - Faulty motherboard given by company

We have purchased an apple ** pro mobile at I store in Visakhapatnam on the *rd of November ****. In the first week of April **** the alarm on the mobile rang. Once the snooze button was pressed, the mobile got switched off all of a sudden and hasn't been working since then. We have taken the mobile to the Apple service center Aptronix where they have declared that it is a motherboard problem and nothing can be done by it. The mobile is out of warranty period but we have not received any intimation for renewal of warranty. When the same was asked they have told that it is the consumer who needs to remember and renew it on his own. Having paid such a huge amount for a leading mobile phone, it is really not possible to remember the renewal date in our hectic schedule. The service centre had acknowledged that it's the fault of the company and not the customer fault in the issue of the mobile's motherboard. We have spoken to apple customer care and they have also told us that the replacement or repair will be done by the authorised service centre. The service centre demanded ***** to be paid to get the mobile repaired and have told us that the phone may or may not function even after getting a new motherboard. I would like to hear from the company. A faulty motherboard is not our mistake. We have run from pillar to post and now we don't even have a guarantee that the phone will work even if we pay the amount demanded by them. We don't have a contact e mail and the customer support has asked us to go through the service centre only. We as a consumer are terribly disappointed as ****** is not a small amount that can be ignored when it is not our fault.