Iphone 12 speaker not working in normal mode (Working when in spaker mode)

My iphone 12 speaker is not working whenever on cal but it works when on oud speaker mode, as per local authorized apple customer support it is the problem with all the iphon12s and i need to give him a original bill and issue will be resolved while i have given them the original bill they are not accepting the bill station that they want bill only from Apple store and not from any retailer.

kindly advise