If you must use a cell phone while you're driving you should:

Pulling off the road into a safe and legal position is the best practice when you need to use a cell phone while driving. This action ensures that you are not actively operating the vehicle while distracted, which significantly reduces the risk of an accident. It allows you to focus on the call or message without the distraction of driving, which is essential for maintaining safety on the road.

Engaging with a cell phone while driving, even if it's positioned in a way that allows you to see the road, still diverts your attention—the mental focus is split, which can lead to dangerous situations. Reducing speed might seem like a safer option, but it does not eliminate the distraction caused by the phone. Therefore, the safest choice involves taking a moment to ensure that you are stationary and in a secure location before using your phone.