What a coincidence! I was just about to call you

What a coincidence! 

A "coincidence" is when something that seems unlikely happens. Here are some examples of coincidences:

• You're vacationing in another country, and you run into one of your friends from college who's on a vacation there as well.
• You check your account balance at an ATM, and the amount of money in your account is exactly equal to the year that you were born.
• Three movies come out in the same season which are all based on the same children's story.

When something coincidental happens, you can say:What a coinclidence!

I was just about to (do something). 

Use this expression to talk about something that you were planning to do next. For example, at work:

A: Hey, are you busy?

B: Actually, I was just about to leave. What do you need?

This expression is useful in situations where you're a little bit late doing something:

A: Hey, can you send me those sales projections?

B: Yes, sorry. I was just about to do that.

This makes it seem like you were already planning to send them soon, even if this person didn't remind you.