Hi ​@Afshin At, welcome on the community. It's possible this change is responsible for that, a part of last month will have the old price, and a part of it will have the new price. On the second page of the invoice you can see everything that was charged on this incoive, including the periode is was charged for. Does that explain this invoice? I can't see what you see, I only know what you tell us.

If it doesn't explain it or if you can't find it, it's best to make a callback appointment (terugbelafspraak). That way a colleague can take a look at this with you.