I forgot to post this.
They emailed me twice since then. One of the emails is a reply (I think) to my question: Why am I getting invoices
Thank you for contacting us.
Our record shows that you initiated the cancellation of your account on March 21, 2013, however your account is minimum contract term and cancellation date will take effect at the end of the term which will be on March 20, 2014. It appears that when you signed up for this account with 1and1, you took advantage of a sale price being offered at that time, and this sale price came with a minimum contract length. When you set your account to cancel, it was processed to terminate at the end of the agreed-upon contract length . Thus, any invoices/charges raised within your contract term or prior to the cancellation are considered valid.
and last email I received was
We are writing to inform you of a matter requiring your attention. We regret to inform you that your current PayPal merchant agreement limit is not sufficient to cover your recent invoice at 1&1.
Please take a moment to log into your 1&1 account and update your PayPal account limit as soon as possible, so that we can continue to offer your 1&1 services without interruption.
I ignored both of these emails.. let's see what happens next