Wedding hair and make up

I was thinking about doing my own make up and just having someone do my hair to cut down on cost but I would rather have someone do it all for me so I don't have to get stressed out on the day, I was just wondering do you have to have a trail or can the hairdresser and make up person come on the day if you know what u want and just do it as this would make it cheaper to have my hair and makeup done on the day than having a trial and on the day costs.

T. I. A
Emma