Honest and Reassuring:
* "Oh, I'm so sorry, that wasn't what I was going for. Let me see if I can fix it."
* "Hmm, I think we can definitely get this looking better. What are your thoughts?"
* "I'm going to try a different technique to get the style just right. It happens, but I'll make sure you're happy in the end."
Humorous:
* (While making a small adjustment) "Just a little trim here and there, nothing major... just like I planned it all along!"
* "I'm going for the 'artfully asymmetrical' look. It's very trendy... I think."
Professional and Helpful:
* "This is a tricky style to achieve, let's see what else we can do to make it work."
* "I'm going to try something different, do you have any ideas on what you'd like to see?"
* "I'm happy to work with you until we get the style you want. No worries!"
Ultimately, a good barber will be honest, professional, and will do their best to rectify the situation to the customer's satisfaction.