I imagine what happened was that the items were free...out the door that day...no upfront cost, but then the info about the monthly additional charges were on the screen you signed at the register.
Sophistry...wordplay. I believe it to be wrong to present a sales tactic that relies on the customer taking the wrap in the end by pushing the blame off within the fine print.
T-Mobile is all about clear, easy, and simple transparency. Seems that no matter how a you look at it, a sale should start up front and end the same. Seems maybe this wasn't the case here.
I haven't found a contact list for T-Mobile myself, which is a bit strange given Verizon's Leadership page does/used to connect you to local, divisional, and regional officers where getting a call-back was at least a 50-50 chance.
M-F 7:30AM PST
This is a most likely outdated list from 2009.
Unfortunately in any commissioned sales environment you will get bad apples like this and even more unfortunate is in my experience you will tend to see it at a store level since obviously the manager either encourages it, demands it or at a minimum tolerates it. Also know that not all T-Mobile stores are "corporate" stores as some are run by third party company as a franchise.
In either case T-Mobile doesn't have a direct email/phone number to call with complaints. Your best way to contact them is via social media and they will respond. Below is the link to get to their pages on FB & Twitter.
Oh man I wish you would have had a better experience with us congojack. If you were told your bill wouldn't go up, there should have been no surprises. You're welcome to use FB or Twitter as suggested above to voice what happened. I sent you a private message you can get to here: https://support.t-mobile.com/inbox
You can reply to that message and I'll report this for you myself. I do understand it doesn't make up for what happened, but I can make sure this is sent to the right department.
Thank you for telling us about this.