Touch tone phones (DTMF) were first deployed at scale in the US in 1963, but they would have been in development at the Bell System for quite a while before that. Possibly also some limited deployments. This ad from 1956 teases a future without rotary dials.
DTMF also led to the rise of Blue Boxes and Phreaking.
“Thank you for calling Customer Service. If you are calling from a touch-tone phone, please press one now. If you are using a rotary dial phone, please stay on the line and an operator will assist you momentarily.”
“We also provide customer service through our website where you can chat with an AI 24/7.”
*pulse dials 1 on the touch-tone phone*