Bad audio FP3+ Android 10 receiving end

Just to clarify: You have a problem with network calls when holding to your ear, not hands free.

Since I bought the phone in Oct 2020 I haven’t had this issue with any version update, only on hands free video(WhatsApp)

Can you use a sim of another network to test it out if it’s a network issue, and if you are using 4G ensure wifi and bluetooth are turned off, as they all use the same frequency band, 2.4Ghz