It's all wrong.
You've interpreted the sentence wrong.
I don't think you're right about it.Rubbish.
I didn't think he's the best in the class.
The answer isn't right,is it?
I don't think it's correct.
I'm afraid it is wrong.
I'm not sure you're correct about the definition
No.it's only a matter of time,actually.
Sorry,that's not correct.
I think I must tell you that your answer is not true.
I'm sorry,but I really should point out your method is not correct.
If I may say so, ifs actually not the case.
If I may say so,your choice is incorrect.
I'm afraid there is some misunderstanding here.
Hang on a minute,…
No,no one is in.
As far as I know,...
Surely .it's him,isn't it?
Allow me to correct one thing you said：...
I suppose it might be more correct to say...