That's odd, @KirstyMM.
Let's try switching off the phone for 20 seconds. While it's switched off, remove the sim card from the phone, and wipe the chip with a clean/dry cloth. Do let me know how you get on.
Same problem for me since update. Contacted Samsung, went through clearing data, soft resets, etc etc. Went into safe mode, tested it by receiving a call and voila its all ok again, the caller can hear me. They said it was an app of mine causing a problem and that I would have to switch on each app individually one by one, receive a call and test to see which app causes the problem. I reminded them that this can not be done in safe mode as all apps are disabled, and also cant be done in normal mode as all apps are on in back ground anyway. I then explained that this is clearly not an app issue as there are no new apps on my phone, and this problem started immediately after the last OTA update so this is an OTA software issue. They then agreed and asked me to report this via Samsung members app, which I have. I asked how long before this is resolved but they said they do not know.....
Incidentally any calls received via any app like Skype, Whatsapp, Messenger etc is fine.
Come one Samsung get your act together, supposed to be the best... Not! This should not happen when you pay £1000 for a phone!!!
I actually explained what the problem was to one of your experts and they agreed with me after giving me the wrong reason for this problem!!! Very bad!