I'm glad that you are loving your iPhone 4! While you are able to connect your hearing aid to your phone, it may not stay connect due to compatibility issues. Please see this link
http://support.apple.com/kb/HT4526 for compatibility details. Also find helpful information about your iPhone 4 http://goo.gl/c9etF online. And you want to take full advantage of your phone's features I recommend a http://vzw.com/workshops free workshop.
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