Switching suppliers is always free of charge. However, you must pay all your outstanding bills up to the final total (if there was no billing based on actual consumption data), which your former supplier must submit to you within 6 weeks after your change of supplier.
Your former supplier is entitled to claim payment of taxes, fixed monthly premiums and any energy consumption until the effective termination of the current contract, even if you no longer consume at the place of consumption. In addition, you must respect the notice period set out in the special or general conditions of your supply contract.
Please note, however, that if your contractual terms and conditions provide for a minimum duration of supply, and you nevertheless change supplier before this deadline, penalties may apply.