I reckon you may have trouble convincing the company to accept your cancellation.
You have a contract with them to supply, based on you paying an agreed price (I assume). Unless the delivery terms were agreed as part of the contract, there is only an element of 'unreasonableness' that you could try to persuade the organisation that they have not fulfilled the contract, thus allowing you to cancel. You are in their hands - be careful or they might take you to Small Claims Court if you try to insist a contract breach by them has occurred.