If my trucks gauge showing that my battery is being charged during driving goes from about 12 to 16 and then drops back again and then back to 16 might the problem be since I recently had it in for replacement of the battery?

Modern vehicles use electronic sensors to vary the charging voltage. If the battery is low it will charge more. If its charged the voltage will drop because the car runs off of the alternator. If you drive it for an hour or two straight you should see the voltage eventually drop to around 12. If you start the engine a lot (like deliveries) it will never get fully charged.

I have a new truck just notice my trucks doing the same no battery change

Could be sometimes it's gd to let ur car run for about 15 mins to make sure the new battery is responding to the other parts like alternator and starter if u feel it's a problem please go or come back to get ur battery checked