Has anyone gotten the 50% off promotion for new iPhone and actually received the credits?

I have wanted to upgrade my phone, and am a new customer - so I am still eligible for the new phone activation promotion. They are running a 50% off promo on certain iPhones. It is actually 50% off because they issue a bill credit for half of the financing charge. Say the phone is $18/month normally to finance over 24 months. They say they will give a bill credit for $9/month for 24 months (thus, keeping you as a customer for the whole 24 months). If you cancel your service, of course, you owe them for the balance. Anyway, the contract/sales agreement they are asking me to sign says nothing about what they have promised. It states that I agree to pay for the full amount of the phone for 24 months. It does not state that they agree to give me a bill credit for 50% off the monthly fee. I asked the rep about this, and he explained that it isn't in writing. It is a promotion, so I basically have to take their word for it that I'll get that 50% credit. I'm trying to find out if anyone else has bought a new phone under this promotion, and are you actually getting the 50% credit each month. See, I am worried that since it is not in writing that I am getting the phone under this 50% promotion, then I have no proof of this. When I start getting billed monthly, if they do not give me the 50% credit, I have already signed an agreement that I will pay full price. In other words, I wouldn't have a leg to stand on, should it come to that because there is nothing in writing of T-Mobile's obligation in this promo. Anyone else out there successfully got this promotion?