When ntering numbers into a customer service telephone numbdr, the screen blacks out

[snafubaby]

When entering numbers into the phone, like bank account numbers, account numbers of utility companies, etc. My phone's screen blacks out sometimes.. it also happens on my sister's SGS3. Does anyone know a fix? I would suuuure apperciate it!

 

[EviI]

Are you entering these numbers into the Dialer app? If so, your hand is too close to the proximity sensor.