Magento Version : 2.1.9
As per client requirement, I want to remove required validation into billing/shipping telephone field while creating a new order from the backend.
so please suggest me how can I do it?
This stackoverflow response is quite helpful in providing a couple of options: https://magento.stackexchange.com/a/163621/26
One is a third party extension to make making it optional easier, or upgrading to 2.2 which seems to have a change to make it easier to be optional too.