You will need to contact Pixel Support.
On your game screen, choose the Settings wheel in the upper corner. Write down your Player ID and then choose the Support button. Scroll all the way down to the bottom of the page until you see a list of categories. (Do not use the white text box in the top half!) Choose a category and then provide your Player ID, and problem details.
If on an iOS device, you might not see the category options on the SUPPORT page. If that is the case, you'll need to email them at: firstname.lastname@example.org