Firstly log into Paypal.
Secondly, click on the options cog.
Go into Payments and 'Pre-Approved Payments'.
After entering your preapproved payments, find Streamline and disable the pre-approved payment.
Note: As of 21/07/2022, when your service is cancelled your PayPal Subscription will automatically cancel. Further changes have been made to monthly services, you're no longer able to purchase a service without creating a subscription, however, cancelling the service will automatically cancel the subscription on PayPal.