Your providers. Once helloBill has set up or switched your services, each one is an arrangement between you and that provider, and they handle your billing, meter readings, payments and the service itself directly with you. So if a bill looks wrong, a payment is unexpected, your broadband drops, or you want to change or cancel something, contact that provider first, using the account details in their welcome email.
If the problem is with the set-up itself, for example a provider has no record of you, your details were passed on wrongly, or you've heard nothing at all, that's us: email [email protected] and a real person will look into it.