General :: Printf White Space - Words Splitting?

I am having trouble keeping the name together and the phone number together, I think due to the white space. I have tried "" and '' it doesn't seem to matter. So it may be my syntax? and does it matter how long the first and last names are.

me$ echo 'fstname lstname' '123 123-1234' | ./myscript
#myscript
read a b
printf "%-15s %20s
" $a $b >> my_phone_numbers
OUTPUT

fstnamelstname
123123-1234
insted of
fstname lstname
123 123-1234

I know its not an elegant script but I am still learning how some commands work.