Whether or not you can get fined for using a hands-free device depends on your age and whether you are allowed to communicate via cell phone while driving.
In states like North Dakota, it is illegal for drivers under the age of 18 to talk on a cell phone while driving, even if it’s hands-free. If you are unsure of the laws in your state, the best practice is to set your phone to “do not disturb” and/or automate your phone to send “not available” messages. Many newer Android and iPhones can send out automated text responses such as “Driving. Can’t talk right now.”