I've been charged something I wasn't expecting.

Payments are collected by your provider, not by helloBill, so the charge will have come from them. Check the amount against what you agreed, and contact that provider first. If the payment was taken in error — the wrong amount, the wrong date, or one you never agreed to — the Direct Debit Guarantee entitles you to a full and immediate refund from your bank. It doesn't cover a charge that's correct but unexpected: getting that money back from your bank wouldn't cancel what you owe the provider, so sort that out with them first. If you're not sure what the charge is or who took it, email [email protected] and helloBill will help you work it out.