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

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 offer TCP and UDP OpenVPN connections?
Yes, and we provide several ports for each type of network topology we offer.
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 a guarantee?
Yes, we offer a money back guarantee. If for any reason you are not happy with LiquidVPN cancel...