If you have been subscribed to a Workable plan prior to July 2017 then you may be on a 'legacy' plan. As long as your subscription has been maintained, you'll have access to all the features which you originally purchased.
If you cancel your subscription, or if there is a lapse, then you will need to resubscribe to a Pay As You Go, Starter or Pro plan. The feature-set may not be the same as your original legacy plan.
You can view your current plan type in the Subscription section of your account, accessed by clicking your profile icon in the upper right.