You should check out one of these, this is what your looking for, they are wireless broadband cards for laptops and work the same as a smartphone data plan, you pay a monthly fee, and only you can use the connection.
Sprint Mobile Broadband Verizon Wireless Broadband AT&T Laptop Connect
These are nice, I would have one personally myself, but they are much more expensive than a cell phone plan. You could also get a smartphone with a tethered data plan. The tethered plan allows you to connect your laptop to your phone to access the internet as a modem, and again, only you can use it. Basically, none of this uses Wi-Fi so your good.