I have had the same problem with both amazon and netflix streaming. Turns out, High definition data (HD) uses enormous data. You need to go to your netflix settings account and set your streaming to Standard Definition (SD). For Amazon, you have to do it to each new show your watching (bottom right corner). Took me a lot of frustration to figure this out but it makes a huge difference. I watch hours and hours of movies with only 50 Gigs per month. Hope this solves your problem.
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