Do you mean...?
If I understand right, ...
I'm sorry if I'm being a little slow, but...?
I'm sorry, I'm not sure I understa12 Do you mean (that)...?
So am I right in saying ...?
If I've got the picture, then ...
So what you mean is ..., right?
Sorry I don't quite catch you. You mean...?
Can I get one thing clear?
Would I be correct in supposing...?
I'm afraid it's wrong.
I don't think so.
I'm afraid what you think about... is not quite right.
Sorry, that's not at all right.
No, you've got it all wrong.
I think the information you have must be incorrect.
If I may say so, it is not the case.
If I may say so, you are mistaken there.
I'm sorry, there is some misunderstandings here.
It doesn't seem correct to say...