Djokovic Series 6-Pack bag as Backpack?

My wife just got me a Djokovic Series 6-pack bag as an early Christmas gift. It's was advertised as having backpack straps, but when it came tonight, I can NOT get it to work well as a backpack at all, no matter which direction I try to wear it. We double checked TW and it says backpack straps, but then I checked Head's homepage and these bags are listed as having a "Dual Shoulder Strap System".

It's important that my bag work well as a backpack also because I ride my bike to the place I play tennis. I see know way to use this bag as a backpack and I am considering asking her to return it for me (which I feel terrible about).

Does anyone use this bag as a backpack?

This is the bag I'm talking about:
Well, I think I've answered my own question. Head lists all of their bags of this style as having dual shoulder straps. I've tried the bag in every possible configuration, and it is possible to use it as a backpack, but it is very uncomfortable and inconvenient.

It's clear to me that head never intended this bag to be a backpack and they don't describe it as such. Checking other bags (wilson, dunlop, etc) that actually have backpack straps built in, the difference is obvious.

So, the only question I'm left with is why these bags are sold as having backpack straps when they clearly were not designed to be worn as a backpack, and are not described as such by the manufacture?