It is a common misconception that an agreement is not binding if it is not in writing. 

In fact, the majority of agreements which give rise to contractual obligations are not written.  Although it is easier to prove the terms a of contract if it is written, a contract which is not in writing does not mean that an agreement concluded verbally or otherwise than in writing between contracting parties is any less binding. 

Contracting parties are bound to respect their agreement and to perform all obligations undertaken by them, whether the agreement is in the form of a written contract or whether it arose verbally or by some other form of express or implied conduct (e.g. nodding assent) expressing mutual agreement.
Irrespective of the contract’s form, if a party does not perform as they have agreed the innocent party cannot merely cancel the agreement (save in exceptional circumstances beyond the scope of this note). A written contact sometimes sets out the procedure which must be followed to deal with the breach, but absent such a clause where a party has breached a contract the innocent party needs to call on the party in breach to remedy the breach before the contract can be either enforced or cancelled.  

Cancellation is a drastic remedy and should not be resorted to lightly.  The innocent party could end up having cancelled unlawfully if the cancellation is premature or if the process steps are flawed.

If you are unsure of your rights we recommend that you seek legal advice and guidance before acting.