Phone field accepts invalid phone number formats

[DragomirStefanaCatalina]

Starting point: http://dev.rohelp.ro/en/admin/hub/ngo/

Expected:
When adding a NGO, Phone field should accept only phone number formats consisting of digits only with or without plus sign.

Actual:
When adding a NGO, Phone field appears as a requirement, though it accepts invalid phone number formats, characters or even email address.