If you require some information you can say:

Could you tell me if/when/how much/why...?

I wonder if you could tell me...?

I'd like to know...

I'd like some information about...

If someone asks you for information you can reply:

As far as i know...

Well,(in confidence,) i can tell you that...

I'm afraid i don't know...

I've no idea,I'm afraid...

I don't have that information available just now,can i call you back?

I'm not sure,I'll have to find out,Can i let you know tomorrow?

I'm afraid i can't tell you that,it's confidentail.