No, no. You can't return a value. That means you can't write
return 5;

But
return;
doesn't return a value, it simply returns control to the caller - that is, it exits the function.

return;
directly followed by the closing brace (}) of the function is redundant.

What do you mean they don't return?
The problem is that you don't give the user a chance to give a different command after one function executed. That means that the
do...while() loop in main is infinite once entered because choice doesn't change.