Unfortunately, the Distance Selling Regulations, where you have the right to cancel, do not apply to B2B contracts only B2C contracts. Therefore, you have no right to cancel unless there is a cancellation period specifically mentioned in the contract documentation. It would be worthwhile checking.
If you do cancel, then you are in breach of contract and the company can claim their loss of profit that they would have earned on doing this over the period. They cannot claim the contract value (although they may try) because they will not have provided the service if you have told them that you did not want it any more.
Provided you cancel very early on, as you have done, it is unlikely that they would proceed to court on this although that decision is entirely up to them. Make sure that you put the cancellation in writing if all you have done at the moment is spoken on the telephone.
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