To use the Magnifier feature on your iPhone, navigate to the "Accessibility" section of your Settings app.

To use conversation mode in the Translate app on your iPhone, you'll need to turn on the "Automatic Detection" feature.

Alternatively, if almost every unknown caller is a dud, you can safely pick the “Silence” option and let voicemail sort them out. This is especially true in an age where number spoofing is rife, where ...