said by PX Eliezer70:
DTMF talk-off issues predate VoIP.
Bell Labs was concerned about this decades ago, and many companies since then....
Female voices are more likely to trigger.
And, the change in a woman's when she gets pregnant can trigger this in certain systems. My brother was working with a tech where this problem suddenly cropped up. He asked, "this is going to sound strange, but are you pregnant?" "Yep." I would have never had the guts to ask. (I hadn't heard the term "DTMF talk-off" but I'm aware of the issue.)