Manually disconnect zap channel

One of our IP phones has been occationally grabbing one of the zap channels and not letting go. How do we manually diconnect the line in software? What’s the easiest, quickest way?

At the moment we’re just having to unplug the PSTN line from that channel and then put it back. That works but there must be a nicer solution.

In the asterisk CLI type soft hangup followed by the tab key it will give you a list of all calls it thinks are active and you can start to type the matching name until it is unique then press tab and return.