VBA Code To Unmerge Cells On Specific Worksheets

I have a workbook with multiple worksheets. On some of those worksheets a have merged cells, so in order to paste new data I need to unmerge them first. Below is the code that I wrote for it. However it doesn’t work and returns “Run-time error '1004': Application-defined or object-defined error”. I looked at this post List Maximum Value From Each Worksheet and tried adding With – End With, but it failed too. As far as I understood the problem is that the Worksheets/Sheets object does not support UnMerge property, but I may be wrong. If I add ws.Activate line (test2) everything works fine.

However I was wondering if there is a way to do it WITHOUT activating the worksheets.

Sub test1()
Dim i As Integer, ws As Worksheet

For Each ws In ActiveWorkbook.Worksheets
Select Case ws.Name
Case "5 - Top Network Facilities", _
"5b - Top Arb Facilities"
For i = 0 To 9
ws.Range(Cells(2 + i * 5, 1), _
Cells(6 + i * 5, 1)).UnMerge
Next i
Case Else
End Select
Next ws
End Sub