Someone just hacked into my contabo account and changed the email.

And Bought 4 VPS worth $1100.

What can I do to get this money back, other than contacting Contabo by email?

The payment method was PayPal, I tried to chargeback through Paypal but it wasn't successful.

Contact your bank and dispute the transaction.
Contact Contabo, if that's an option, and ask then to do an id verification.

Well, that's fd up. Ask for their support, and they will fix it for you. They must be able to check the IP from which the hacker logged in, and they might help you cancel those VPSs and refund the amount. Do you have any idea how you might have been hacked? Do you use the same password elsewhere?