If people can't tell the difference between 12 O'clock in the Afternoon and 12 O'clock Midnight then they need to go back to School to learn how to tell the time. The difference between each time is pretty obvious.
But you are adding to the confusion by referring to 12 o’clock in the afternoon! It is 12 NOON (or midday) or 12 Midnight.
Too many people and organisations these days refer to ‘12 AM’ and ‘12 PM’, which have no validity and lead to confusion, especially where the services concerned operate around the clock!