You didn't explain what you are trying to do, and it's not clear from your code what you are trying to accomplish.
Your code says:
Take the value in cell c
Change it to all uppercase
If you find the string "Aaaaa LTD" in the result, then change that string to null.
If the resulting string is not the same length as the original (implying that the string was found and changed to null), then clear the entire cell.
You will never find "Aaaaa LTD" (or any of those other strings) in a string that has been converted to all uppercase.
If you are looking to clear any cells that exactly match any of those strings, then I would do this:
If you are looking to clear any cells that contain any of those strings, then I would do this:
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