Reduce quality in Netflix for iPhone?
Yes, Since a lot of providers have bandwidth caps, Netflix has put in a downgrade quality option to manage video quality.

Login to netflix first, then go to
https://account.netflix.com/HdToggle

Select from


Good Quality.  up to 0.3 GB per hour. 
Better Quality.  Up to 0.7 GB per hour. 
Best Quality.  Up to 1 GB per hour, or 2.3 GB per hour for
HD.