How to replace xml string with special character in file

Question

So I have .xml file and I want to replace first xml string which says
<some text="chageThis"> and I want to replace it with <some text="NewText"> and I need to specify path of my file in .sh scrypt. I tried from here

sed 's/file="[^"]*"/file="\<some text="chageThis">/' /path/to/my.xml > /path/to/my.xml 

but it does not work