This sounds very much like my issue.
In early January of 2014, I took my brand new iPad Air and couple year old iPad 2 (compatible version, per the website) into a T-mobile store to get this promotion. I ask the rep for the Free 200MB for Life Data plan and said that I understood I would only need to buy the $10 SIM cards for the devices. He had no idea what I was talking about and asked another rep. They pulled out some paperwork and muddled through some questions, took my license, etc, and sent me on my way with 2 new SIM cards in the device and an account supposedly setup. About 2 weeks later I get a bill for $20. I call customer service and they basically tell me the store set me up incorrectly as a post paid customer and I need to be a prepaid customer to get the Free Data for free (funny). So I needed to waste my time by going back to the store to get 2 new SIM cards for prepaid accounts. I did this and came home and activated them. No 200MB Free for Life Data for my iPads. So, I call in again and find out that when they setup the new cards they didn't give me the PINs. So, I now need to go back to the store so they can verify my identity and make sure my IMEI numbers are correct in the system. I did this and still no service. Over what is now 2 months, I have made MANY calls in to customer service and been told numerous things like "because I was activated previously, the system won't let me activate again as a prepaid customer and give me the promotion." So, they gave me some help desk ticket numbers, told me to wait 72 hours and it would be fixed. Waited 72 hours, not fixed. Call in and give them the ticket numbers. They say those numbers aren't help desk numbers. Hmmm. So, they also tell me that the post paid to prepaid activation doesn't matter and it isn't correct. They try canceling the accounts, verify the IMEI, SIM card, phone numbers, and a bunch of other stuff. They then tell me that they would put in a help desk ticket and it will be fixed, just wait up to 72 hours. Waited 72 hours, not fixed. Call in again, still don't know what my ticket numbers are. Go through again with the resetting of accounts, verifying IMEIs, SIM cards, etc. This time the agent says that he can clearly see that my iPad air is setup with 200MB service, but it could take up to an hour for it to take effect. That was yesterday, and guess what? You got it, still not working. So, I call in today and went through similar conversations where they wanted to cancel the account and start again. I said that doesn't work, so guess what again? Help desk ticket e-mail to someone about something for both devices. I am told it will be resolved within 72 hours. I have 0 faith in that happening. There is obviously something wrong with my account since both devices are doing exactly the same thing. This needs to be escalated to a system admin person with the appropriate rights to correct my account. Absolutely ridiculous. This should have been a real nice thing, free data for life, but instead is a nightmare. I just wish someone somewhere at T-Mobile had the proper authority to solve this issue. The constant canceling the account, help desk and wait 72 hour thing isn't working.
