hello at apple.... I got invoice on my account for app that was free for 2 week

Does the app offer subscriptions? A lot of apps with free trials will automatically convert to a paid subscription unless you cancel the trial before the end date for the free period.

Check your subscriptions -> Manage App Store purchases, subscriptions, settings, and restrictions on iPad - Apple Support

We’re just customers like you. You’ll first want to follow https://support.apple.com/en-us/HT202039

Then follow https://support.apple.com/en-us/HT204084