Sorry to hear of the issue.
The issue is, if you signed at their premises, there is no automatic 14 day cooling off period.
A cooling off period only applies if :
1. you paid / signed up "at a distance" such as online or by telephone, or if they came to your house
2. if you did not sign "at a distance", there is a contractual term which gives you 14 days.
You would need to check what it was you signed up to see if there is any cancellation term and any cooling off period.
The only time a contract could be void is if you were misled, i.e they told you something false which induced you to sign up. Or if they force you to sign under duress. Or if the contract is heavily weighted in their favour making it unfair. Or if the service is illegal, for example.
If none of the above apply, there is then a binding contract in place and they could sue you if you stopped paying.
If any of the above scenarios did take place please let me know and we can discuss further but as it stands I fear you may be bound to what you signed up to.