Hi Jarrad,
The checkbox and statement is not necessary for a contract to have been made. In every contract, even if there is no express provision that states the parties have fully read and understood the agreement, there may still be a legally enforceable contract in place. So long as the elements of a contract are in place — intention to enter into a legal relationship, offer and acceptance (agreement), consideration (money paid and services rendered) — there is a contract in place.
There are circumstances that vitiate or invalidate a contract. However, not reading or actually understanding the terms and conditions is not one of them. The test is objective and would go toward the parties' capacity to enter into an agreement. Cases where this has succeeded are those where one party does not understand any, or understand very little, English, is of low education and of very little business experience of the kind of contract entered into. In this case, the argument here is not that there is a contract that should be set aside, but that there was no contract in the first place because one of the parties had no capacity to agree and could not have held the requisite intention to enter into legal relations. It is dangerous to make "no contract" arguments because then, any obligation by any party under the contract would not exist, including your ability to enter (or have entered) the gym and use its equipment.
Having said that, you may try and lodge a dispute with the
NSW Department of Fair Trading and see if you can negotiate some kind of termination procedure/policy with your gym. They have an
information sheet on gym memberships. If your gym is part of
Fitness Australia, you can try contracting them and asking them to resolve your dispute. If not, you can ask the Department of Fair Trading to assist you with the matter. They are a free service and are able to conciliate resolutions between consumers and businesses.