Hey woman! Kay, "unlimited data" that is just space, right? Not internet and SMS? Am I just not getting this?
Unlimited data is all-you-can-use Internet, streaming, downloading, uploading. All smart phone plans offer some combo of voice (phone calls) and data. Some plans include unlimited SMS; some count them separately from data and voice and allow only so many SMS, or charge per SMS.
If you're in the field, it sounds work-related. Doesn't your company pay for your plan? If your needs are similar to your co-workers, it'd be good to ask them about their plans. Some carriers offer good reception and data speeds in only certain areas, so you don't want to unknowingly sign up with a dud carrier for two years. If you already have an unlimited carrier, it might be as simple as keeping your plan and switching your phone.
Some companies also have deals with carriers, so employees can get discounts, subsidies, etc. My company, for instance, offers 20 percent discounts for at least two carriers, and the discounts apply to every phone in your household. (This is separate from company-issued phones and their plans, which are billed directly to the company.) The company offers a discount code, you sign up once with carrier and your bill is discounted every month. If your company doesn't have plans, you might suggest they look into getting one.