You don't have to disable it. There are actually both functions available. The main microphone you see next to where you begin entering text is the voice recorder. If you hold this down it will record then send immediately when you release. There is a SECOND microphone down at bottom left...
I have samsung s7 and am using message+ that came with phone for texting app...I do not see an option in settings to select SD card for storage. Racking my brain! Any other ideas ??