voicemail after landline cancelation

“I am not reporting a dialing problem. This is a recently disconnected Xfinity Voice number. Callers currently hear ‘Your call cannot be completed as dialed,’ which makes them think they dialed incorrectly. I need the number’s intercept treatment changed to a definite disconnected-number announcement, such as ‘This number is no longer in service.’ Please send this to the Xfinity Voice provisioning or telephone-number administration team.”  My mom will  keep trying and trying if this can't be dealt with-thanks