access a Database scalar value function in Entity framework 6 within linq

What steps i should follow to use the following sql scalar value function within entity framework.

select dbo.GetDefaultAccount(5,1,48)

I tried creating a static class under the same namespace of the edmx and defining the function as following

    [EdmFunction("Model.Store", "GetDefaultAccount")]
    public static int? GetDefaultAccount(int id, Int16 type, int assocId)
    {
        throw new NotSupportedException();
    }

While accessing it from linq like below

  var Accountno = (from s in dbcontext.TranSetups select new { Accountno = CutomEdmxFunctions.GetDefaultAccount(5, 1, 48) })
                       .FirstOrDefault().Accountno;

I get the following error

cannot be translated into a LINQ to Entities store expression because no overload matches the passed arguments

Thanks