Mixed signals from a phone account order

Yesterday a new phone line was added to my household account during a busy day, so I didn’t spend much time going over each part of the agreement. When the confirmation arrived, the total on the account page did not align with the amount that seemed clear during the initial sign-up. Extra features appeared on the summary that no one remembers selecting, which makes it hard to tell whether the order process added them or someone clicked too quickly. Since the next bill is coming soon, I would rather clear this up calmly instead of waiting for a surprise charge. How do others approach this kind of confusion so that fees can be explained without turning the whole situation into a stressful argument?