Although we don't have a feature to never allow clients to cancel online, we do have a little trick with your scheduling policies to help handle this.
Here is the deal: just set your Cancellation Policy to be at least 1 day longer than your Client Scheduling Policy, so that clients can't schedule online out into the future far enough to be able to cancel online.
For example, if your Client Scheduling Policy is 1 day, setting the Cancellation Policy to 2 days will do the trick! These policies can be edited under Settings > Policies in your Schedulicity Dashboard.
Read our blog on creative ways to reduce no-shows and cancellations here.