If you want to pause interest, go to Plan new activity in the activity panel. After this, click on Pause interest.
You will come to the pop-up window as below. You have two options: pause the interest from today until the day when it starts again or option 2: indefinitely. If you go for option 1 you need to indicate the resume date from when it will start again.
Do not forget to press on the Save button.
You can see that the interest calculation changed in the activity panel.