By the sound of it you’ll need to replace the microphone. But in the case of the S10 lineup samsung made that harder. In previous models and models after the S10, the charge port which contained the lower microphone was on a separate daughter board which could be easily changed out. The S10 lineup has the charge port and it’s components directly soldered to the mainboard so you most likely won’t be able to DIY this repair without causing significant damage to your device. You could try to send it to a board repair specialist like Jesse from VCC Board Repairs or Jessa from iPad Rehab. They both have youtube channels you can check out and I personally use VCC for all of my board work since I’m not equipped to handle those repairs quite yet.