I'm so sorry to hear about your phone, having one stolen is such a bad situation.
So you're saying that you bought a replacement back in February after the original device was stolen and didn't realize that you had insurance until now? I'm really really sorry but it's well outside of the buyers remorse period for the purchase of the device.
My guess (and please forgive my own assumption) is that the employees you had spoken with assumed that you were aware you had insurance but wanted to upgrade your device anyway, especially if you were aware that you had Apple-care with it (which can't be purchased as a stand-alone, only as an add-on to the insurance plans for Apple devices). It's the most likely explanation, though I'm sure it doesn't relieve your frustration and for that, I'm very sorry.
If anything could be done, I would reach out to T-Force via Twitter or Facebook and fill them in on the situation.
its not stolen
my iphone 6s can you tell me if its under warrenty threw apple
Hey there! I'm terribly sorry but as this is a community forum, no one here can access your account. Is your phone missing or is it acting weird? If it is missing or damaged, you'll need to file a claim through your insurance company, which is likely Assurant who can be reached by calling 866-866-6285. If you have a broken screen and have Apple Care, you can get it fixed for a $29 deductible.
You can check your coverage by logging in to my.t-mobile.com and selecting the Plan tab at the top. You could also reach out to care by dialing 611, use the Message Us link on this page, or heading to T-Force via Facebook or Twitter.