To cancel your subscription click the VPN Administration button on the left hand menu of https://my.liquidvpn.com/clientarea.php 
Click VPN Administration 
Click the service you want to cancel
Click Request Cancellation
Choose to cancel immediately (takes up to 24 hours to process) or at the end of billing period
Either option will stop your subscription before being billed again.

Also Read

Can I use LiquidVPN on a mobile device?
The short answer is yes However we have not released our mobile VPN client yet so you will need...
What kind of encryption does LiquidVPN use?
LiquidVPN implements the highest level of encryption natively supported by each of our VPN...
Do you block any ports or types of traffic?
No we do not block any ports out right. Port 25, 22, 21, 23 are monitored for abuse, if our...
Do you offer TCP and UDP OpenVPN connections?
Yes, and we provide several ports for each type of network topology we offer.
How do you handle abuse?
When an ISP sends an abuse report we will post it on our transparency reports along with our...