No call waiting beep

I've noticed this since I got the phone, but calling waiting doesn't beep ever. It just shows missed call after I hang up. I was on speaker phone starring at my phone for a 3 minute call and I didn't even see anything come up regarding a second call coming in. When I hung up it showed it.

Any ideas how to problem solve this?

Mine works fine. I bet it's a carrier issue.

I get a chirping sound (more like beeping) when someone is waiting.

Via my Z10

I'm on T-Mo and I get a beep and a visual notification on the dialer screen.