Unlocked iphone 5S Hotspot Not Working, Unlocked iphone 5S Hotspot Not Working

I have a factory unlocked iphone 5s with IOS7.1

When I try to turn on the hotspot a window pops out on the screen saying "To enable Personal Hotspot on this account, contact T-Mobile at 1-800-937-8997 or visit http://offers.t-mobile.com/tethering/upsell.do". I contacted Tmobile customer service and they told me that all the settings are good on my account and I do have hotspot feature included in my monthly plan. I am supposed to be able to use hotspot feature on my iphone with no problem.

My question is, is the problem caused by IOS 7.1? Any way to fix this?