Hi, in the last 2-3 months I’ve had similar problems - on a very old FP - with calls where the person I’m calling cannot hear the caller. More than once the solution for me was to request a replacement simCard from my service provider. Seems that quite often the vodafone/o2/ee powers of this world mess about a lot with server/comms settings at their end, and the most straight forward solution for us victims is to request an ‘up to date’ simCard that is more compatible with setting alterations.
See if that helps before fiddling with likely ok mics on your device.