This is the exact problem am facing right now and godday seem not to understand the problem and give their customers a right answer and how to fix it. My website does exactly the same thing as yours, it opens with https://www.myphoneprices.com but does not open with https://myphoneprices.com please don't forget to post how you solved the problem when you do. Thanks
Take a look at these instructions from the Blogger side of things. Be sure you have completed everything with Blogger, in step 3, with attention to number 8. This will allow Blogger to redirect the domain. Also be sure you have created the "www" CName at GoDaddy. The host name for the "www" CName record should be "ghs.googlehosted.com" (no quotes on either).