When the subscription is inactive (or canceled), the TextApp reserved number will no longer be available to anybody (including you). Call history and all the messages will likewise be lost.
Are you one of those who want to preserve WiFi and/or Sim number(s) with a little fee, instead of paying in full - just to reserve your number for yourself? If so, please raise a request through this site using + New Support Request. We will prioritize such features if we get to hear from more people.