motherboard not under warranty because worn out after 16 months?

good day I would like information, I bought an iphone 11 128Gb 16 months ago, now the network no longer works for an update, brought to assistance through the dealer tells me to have to pay for the repair of the device as the maintenance of the motherboard it is due to the wear and tear of use. Can the motherboard be considered worn after 16 months and therefore have the buyer pay the cash? does the seller's guarantee not prevail?

Thank you