You have full control of your subscriptions and you can cancel any subscriptions at any time within your account.
In order to do this, you will need to log into your account and go into the Financials section.
Once here you will see the 'subscriptions and alerts' panel where you can view your purchased Keywords and Longcodes (txtUs) numbers.
Alongside these under 'Action', you will have the option of unsubscribing.
Click on the link below to learn more