I'm on Sprint. Yesterday I received a call from (999)-999-9999. I was busy at the moment so i didn't pick up. Few minutes ago I got a call from my own number. I picked up the call, and an automated voice said "Press 1 to accept, press 2 to send a voicemail." Out of curiosity I pressed 1. Then there was nothing, so I hit the hang up button but the phone app did not hang up and close for another 30 seconds. I'm wondering if this was a hack/hack attempt on my phone?
Has anyone else experienced this?