Voice Mail Indication

We recently replaced our old Uniden 2.4ghz phone for their newer DECT 6.0 System which is 1.9ghz. Since the change the voice mail "Light Indicator" on the handsets don't blink on the handsets when we have a voice mail waiting. 

According to the manual the VM system must use "Frequency-Shift Keying" for this notification to work.

Does Cox use is type of message notification or am I out of luck just looking at my phones to know if I have a VM?

Picking them up an listening for the "Stutter" is getting old and I am missing returning VM's in a timely manner.

Thanks.