During a recent CRM course, our instructor reminded us that we make on average 30 errors a day. It is ok to make mistakes, in fact it is human nature to make mistakes. When we recognise a colleague has made a mistake and it needs clarifying then we speak up, but it is important we do it in a way that is both professional and respectful. I can guarantee they will be doing the same to you later on, the skill of a professional therefore is not to get all high and mighty about how they made the mistake of calling it "Flight level 17,000" rather than "Flight level 170". It's a great example though and one that would need clarifying, I can just hear myself now "did ATC clear us seven thousand, seventeen thousand, flight level?" So we would get back onto the controller to ask, and then ensure we both had the correct altimeter setting and cross check them.
This forum has a terrible culture, some almost taking a smug pride in pointing out others errors. Thankfully where I work it's all about "nuture". It's a heck of a lot easier to admit mistakes to your colleagues and yourself when you know you wont have to defend yourself like you have to on here.