Getting a new iphone 5

Hi ! I`m planning to get a new iphone 5. I lost my iphone 4s (with softbank contract) few weeks ago. Is it cost effective/cheaper to get iphone 5 via au, rather than soft bank ?
If it is cheaper, i think i will terminate my old softbank contract and change the carrier to au. Since I didn`t find any english speaking staff in au stores, I`m having problem in getting adequate information. Guys , Could you please help me out? Suggestions please!

This page will help you (use Google Translation if you need)

=> au窶堙?箪ﾆ稚ﾆ暖ﾆ弛ﾆ停?愴誰窶堙景Phone窶堙戸?｡窶堋｢窶堙債？

Better yet, go to both Softbank and AU with a Japanese speaker as they often run special campaigns.

I don't know if they still have this offer, but I got an iPhone 5 free from Softbank a few months back. I simply needed to redo my contract and extend it for two years. It didn't matter how long you are a customer, as my wife switched from AU and got the same deal at that time. You should check it out.