Motherboard failure

Please take a look at iPhone 8 Logic Board Replacement Program - Apple Support and check your iPhone serial number using the tool provided in the support document.

If this potential solution does not apply to your phone Apple provides a standard 12 month warranty. We don’t know where you are in the world, so browse to https://www.apple.com/legal/warranty then drill down as appropriate to your device and location. You could also seek your own legal advice if you wish to find out what your local consumer law provides in your location.

Although Apple is entitled to stick to the 12 month warranty I personally find that harsh and unusual, I’ve had a few laptops that have had issues just outside the warranty by a similar amount and never had a problem getting it sorted.

You may have come upon a particular strict Genius or have experienced a clash of personalities, but whatever the reason did you escalate the matter first to the store manager and failing that through customer services.

Another thought is some regions now have a greater than 12 months guarantee, Europe and the UK for example, did you highlight that if it applies and what was the reaction.

I believe unless your country offers the greater period of consumer protection you may have to prove it was a latent fault, it basically existed from manufacture and has just took time to develop, may be the independent report might go some way to supporting that theory.

I really can’t add much more I’m afraid and you will need to confirm the consumer law in your location, but if you can re-open a dialogue with Apple that would be my preferred option, explain you feel their decision is unfair and considering the nature of the fault it should not be happening in such a short life span considering the premium status of their products.

But, all bets are off if the device has any visible signs of abuse or any internal customer damage, best of luck and hope some of this helps.