Created Unassigned: System.ApplicationException: Column Length must be between 1 and 3. [9206]

When I run this code (there is Data column in my sheet)
```
Console.WriteLine(ws.Cell(2, "Data").GetString());

```

I get this exception
```
Unhandled Exception: System.ApplicationException: Column Length must be between 1 and 3.
at ClosedXML.Excel.XLHelper.GetColumnNumberFromLetter(String columnLetter)
at ClosedXML.Excel.XLAddress..ctor(XLWorksheet worksheet, Int32 rowNumber, String columnLetter, Boolean fixedRow, Boolean fixedColumn)
at ClosedXML.Excel.XLWorksheet.ClosedXML.Excel.IXLWorksheet.Cell(Int32 row, String column)
at ObslugaExcela.Program.Main(String[] args) in e:\DATA\CS-solutions\Polkomtel\ObslugaExcela\ObslugaExcela\Program.cs:line 29

```

I am using .net 3.5