pronouncing each digit indvidually from dialpaln

I've a 10 digits telephone number in the dialplan in a variable, say $xyz.
if I use, same=>n,swift("${xyz}), swift pronounces in billion, million etc. How can I tell swift to pronounce each digit individually?
if I use, same=>n,swift("${xyz}), swift pronounces in billion, million etc. How can I tell swift to pronounce each digit individually?