Hairdressing trail? help?

Well on saturday i have a trail at a hairdressers, the prices are quite expensive. So i don't want to look over the top or 'cheap'. I was thinking of wearing black brogues, black trousers, but i don't know about the top. On the phone the owner who i was talking to said wear black but i cannot remember if she said white as well. I have a white top with detail on the top which i think might be acceptable. But i don't know if she said just black, and i only have like 2 black tops which are just plain tank (Primark) but i think that would look too plain. I'd go out to buy something to wear but at the moment i have not got any money as i do not have a job. Should i just wear the black top to play it safe? And also have you got any advise to carm my nerves before i go in e.g. what to say when i first walk in the door ect. Thank you! :)