You can always switch energy providers whether you're coming to the end of a contract or even mid-contract. Exit fees only apply when you are within 6 weeks or 42 days of your contract end date (varies per energy provider) so you have time to research a new tariff and switch well before your current contract is up.
Even if you are mid-contract and exit fees apply, Onedox will notify you of how much you’ll save if you switch now. You can still save even after paying exit fees.
It always makes sense to keep your options open! It's standard practice for energy providers to roll you on to a more expensive tariff once your fixed contract ends, so make sure to switch tariffs first so this doesn't happen to you!