How to Cancel a process using Process manager

Can anyone help us on how to cancel a process.
We tried using Process manager

ProcessManager processMngr = new ProcessManager(clientFactory);

The completeProcess() method is not getting displayed in the processMngr.

But It is given that
processMngr.completeProcess(invocationId) - will complete the process.

The jar file is imported properly. We double/triple checked it.

Why is this problem coming. Or is there any work around to complete the process.

Thanks,
Sara