VT7 - problem with '0' at the beginning of value of field

1 - add a value in a field (I test on text and phone field) beginning with '0'
2 - go to edit, remove 0
3 - save
RESULT: 0 it's not removed

or

1 - add a value in a field (I test on text and phone field) not beginning with 0
2 - go to edit, add a 0 at the beginning
3 - save
RESULT: 0 it's not added