Why can't I cancel the purchase number MM5T1LJBTJ ? I did not want to make this purchase, please return my money

As stated above, we’re not Apple. We can’t help you. Here is what Apple suggests for viewing and changing orders:

Viewing & Changing Orders - Shopping Help - Apple

If you can not do what you want via that information, use the Get Support link in the upper right of this webpage, and discuss your request directly with Apple:

User to user support forum.

Nothing we can do for you.