Hello,
In the Web Interface, only operations permitted by Security Roles are displayed to a user. That is, if a Security Role does not allow a user to perform a certain operation, it will not be available in the Web Interface. Thus, to remove the operation from the Web interface, you need to adjust your Security Roles so as to not allow users to perform Exchange Tasks.
Optionally, you can also disable Exchange Tasks in the Web Interface completely. For information on how to do this, see point 4 in the following tutorial: http://www.adaxes.com/tutorials_WebInte ... bjects.htm. In your case, you need to clear the Exchange Tasks checkbox:
As for the Telephone Number (Other) attribute, it is not possible to forbid adding values to it. You can only allow or disallow editing the attribute. Here, again, you need to adjust your Security Roles to remove the appropriate permission.