Sound muffled

Hey folks I just got the IPhone XR am3 days ago I do love it but every time that I make a phone call people tell me I sound muffled, WhatsApp and Skype and all are perfect and so is my camera, also I can hear people perfect,I have re set my phone, cleaned the speaker, taken the case off, made sure that there was no plastic on the phone and still the same issue, can someone please help because Apple support suggested I send it back but I don’t wanna to be phone less at the moment and think it can be easily fixed. Much love Scotty