how do I send phone back for check up

[AC Question]

People cannot hear me on my phone unless I put it on speaker.

 

[Law2138]

Please be more specific with your situation:

Provide your type of phone, brand/model, carrier, country, date of purchase, etc. The more information you tell us, the quicker we can provide some tips.

Based on your question alone, the only thing I can think of is a factory reset or make sure you're not connected to some BT headphones. (I've left them on in my gym bag while still connected to my phone.)