Tired of Amazon Prime? Canceling it might not be as straightforward as you think. Here's what you need to know.

Starting Oct. 1, Amazon will change its program that allows Prime members to share free shipping benefits with people outside their household.

A hefty $1.5 billion of the total will go toward customer refunds for those who enrolled in Prime without their knowledge or were unable to cancel.

The change comes after a report that Prime signups leading up to its Prime Day event — which was extended to a whopping four days this year — were down compared to previous years. According to Reuters, Amazon missed their projected goal by about 2 percent.