Automatically switch from external speaker to handset speaker on your phone by bringing the phone close to your ear.
Smart speaker switch on OPPO A37 (A37fw) is as follows:
Step 1: Navigate to settings and choose gestures and motions.

Select gestures and motions.
Step 2: Choose smart call.

Choose smart call.
Step 3: Turn on the speaker switch feature.

Enable the speaker switching feature.
Wishing you all success.
