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

What kind of encryption does LiquidVPN use?
LiquidVPN implements the highest level of encryption natively supported by each of our VPN...
Can I use Bittorrent and P2P?
Yes, LiquidVPN fully supports bittorrent and P2P on all of our servers. We will never censor P2P...
Where is LiquidVPN located and what are your countries logging policies?
LiquidVPN is located in the United States. The United States does not have any logging policies....
What countries are you have VPN servers located in?
LiquidVPN maintains VPN infrastructure all over the world. We select the best regional hotspots...
Do you limit users data usage or bandwidth available?
No, LiquidVPN will never impose bandwidth restrictions or data caps on a user. In fact we...