It depends. If the amount you owe is very large, or large in respect to how much you're usually billed for energy, we might not be able to flip you before the debit balance is cleared.
If you have a debit balance and we flip you anyway, your former supplier might object to you leaving.
The safest bet is to clear any debit balance with your supplier before you sign up.
If you receive an objection we can discuss with you what may be best for you and you options, if you contact us.