Can I POST in JSON formatted body to Epicor P21 through API callout?

Hi, I just wanted to confirm if it’s possible to POST records to Epicor P21 through API callouts where the the body is in JSON format. I have been trying to POST customer records from postman and they work fine when the body is in XML format, but doesn’t work with JSON formatted body. Is it just not possible or could I be missing something?
Thanks in advance!