ComboBox Dependent filtering RowSource property error

I currently ran into an issue where I cant get the data in a ComboBox to filter correctly. I currently receive a Run-time error '380': Could not set the RowSource property. invalid property value.

If i Filter the first ComboBox by 11503 It will throw the error leading back to

Me.PhaseNumComboBox.RowSource = "11503"

PhaseNumComboBox Row Source is Data!C2:C50 and JobNumComboBox Row Source is Data!B2:B50

My data is also repeating so the jobnum will have multiple 11503, trying to show all Phases linked to that job number.

Private Sub JobNumComboBox_Change()

    Select Case Me.JobNumComboBox.Value
        Case Is = "11503"
            Me.PhaseNumComboBox.RowSource = "11503"
        Case Is = "11588"
            Me.PhaseNumComboBox.RowSource = "11588"
        Case Is = "11503"
            Me.PhaseNumComboBox.RowSource = "11503"
    End Select

End Sub