Not if you had one of the pre-existing unlimited data plans...

Just switched to T-Mobile last month: much better experience than what I had with Verizon so far.

I drank Red's 4G flavor-aid early and gave up my unlimited plan. The map said I was in 4G range but my pricey modem disagreed. I switched to Tmo two years ago and love it...better than expected coverage in metro areas, 1/2 price and unlimited everything.