I don't believe they can just start the data again. The only way this might be possible is if they moved your monthly data cycle ahead, but I don't know that they can even do that. I know that they can sometimes give a few data tokens to help, but other than that, data used is data used.
The following posts might be beneficial to you. They concern data usage, and ways to conserve as much of it as possible.
Edit: I misunderstood. I thought you meant you had gotten the upgrade a few days ago and had exhausted all of the new plan data since then, and that the phone rep said that they would reset it to start it again today. I see now, from Liz's post, that this was not the case. So, please disregard my reply.
I see it's your first post here, so welcome to the community! I pulled up your account to investigate and I see that you are indeed on your new 30 GB plan with your data refreshed:
If you have any other questions feel free to reach out again.