Removing Outside Grid Border

[Neil N]

I've been trying to remove the thin white border line with no luck,  Any help?

                            <telerik:RadGridView
                                Margin="0,5,0,0" AutoGenerateColumns="False" BorderThickness="0" BorderBrush="{StaticResource LaGrey12}"
                                ColumnBackground="{StaticResource LaGrey12}"
                                GridLinesVisibility="None" IsReadOnly="True"
                                ItemsSource="{Binding ContactActivityNote.ContactActivityParticipants}"
                                ShowColumnHeaders="False">
                                <telerik:RadGridView.Columns>
                                    <telerik:GridViewDataColumn
                                        Width="Auto"
                                        DataMemberBinding="{Binding ParticipationTypeId}"
                                        Header="Type" />
                                    <telerik:GridViewDataColumn
                                        Width="*"
                                        DataMemberBinding="{Binding AddressedTo}"
                                        Header="Addressed To" />
                                </telerik:RadGridView.Columns>
                            </telerik:RadGridView>

[Dimitar]

Hi Neil N,

I have checked the default theme, but there is no border. Can you specify the theme used? Can you send the XAML of the entire window as well? 

Thank you in advance for your patience and cooperation.