Tell us what you were doing and what happened, and whether you were using the website or the Windows application. That is usually enough for us to find it.
Please do not send passwords or connection details. We never need access to your database — the questions we can answer are about the application, not about what is in your data.
Billing, receipts and cancelling are on the Billing page. To see what we hold about you, or to have it deleted, ask here — the Privacy Policy says what there is.