Pass (Send) persian string as Parameter to StoreProcedure in SQL Server

hi

I use the drop-down list in the page that bind Items from database

when users select an item from the dropdown list and click the button it will search data from database and shows in gridview below is SP:

ALTER procedure [dbo].[ViewphoneInfo]
    @Group1 NVARCHAR(40)
as 
begin
    select *
    from phoneBook
    Where Group2=@Group1
end

but here when users select Item('مستاجرین') --> it is Persian word from dropdownlist it doesn't show result in gridview:

I test SP:

use AmlakeAbdi
select * from PhoneBook
where Group2='مستاجرین'

It works correctly and I checked selected item from dropdownlist it selects correctly but it doesn't show data in gridview.

I think it didn't work correctly because I use Persian word in dropdownlist I had the same problem in the database but when I wrote(N) like:

data=N'تست'

it works correctly but here I don't know what should I do?

Best regards

Neda