Because you would now be on an AT&T plan which no longer offers unlimited data. Other people got it because they have been with AT&T long enough to have it grandfathered.

I'd get in contact with Jamileh, one of the Community Managers, and see if she can't help you out. Not sure how the grandfathering for unlimited data works with Alltel customers. One thing you didn't indicate in your post is what KIND of phone you have. If you have a feature phone with unlimited data, then you are most likely out of luck. If your current phone is a smartphone, then you might be able to get a new smartphone with unlimited data. It wasn't a blanket unlimited data grandfathering that AT&T allowed; you had to have a smartphone data plan on your account prior to the plan being retired.

Still can't get it though, he had an Alltel plan which doesn't carry over when switching to an actual AT&T plan

I came over from Verizon and they grandfathered my unlimited data plan.  I did have a smartphone with Verizon though and now I have a Motorola Atrix with unlimited data.

When did you come over and if it was recently someone went over policy to make a sale more than likely

I have had my original Alltel Plan for 11yrs now. The only way I've been able to keep it, is by keeping the same phone number no matter what. The only issues I've had so far (this month) is that back in Nov. 2011, when I upgraded to a Verizon telephone, the code to my texting option was not compatable to the new phone....which they didn't tell me right away and so I've been texting all these months and paying for each text. They were good to recognize the problem and try to remedy it within 2 days, but I admit I was a little frustrated. So now I pay $10 for texting I used to get for free... Also, when Verizon took over Alltel in 2008, I had just signed a new 2yr contract, and I went and additional 2yrs with no contract until I upgraded phones. I probably could have continued that way had I kept my old phone.

Don't even bother trying to get AT$T's unlimited plan grandfathered.

They are pushing us all out the door.

I've had unlimited data for over 15 years.

Now once I hit 2 Gbs, my phone turns into a brick for the rest of the month.

And to maker matters worse, they were unable to unthrottle some users (myself included) when their new billing cycle starts.

I'm not paying $200/mo for a fricken paperweight!

Good riddance to this crappy service!

Weird, I'm on 5GB, no throttle yet