When you make a Charisma ability check that you are proficient in you may choose to take a 20 rather than roll a d20. If the check would be made at disadvantage you take a 15 rather than a 20. If you are speaking creatures must be able to hear you, or if you are gesturing creatures must be able to see you, for this ability to have an effect.
You have one use of this ability and you regain expended uses on a long rest.