“Did I catch you at an OK time?”
You're a salesperson. You're calling a client to try to pitch them on a new product that you're selling. You check to make sure that the client isn't too busy when you call.
Did I catch you at an OK time?
To "catch" someone means to get a chance to speak with them.
A: Have you asked Tony about getting you access to the expenses database yet?
B: No, I wasn't able to catch him yesterday.
Oh, I'm glad I caught you. I have a question...
You can use this phrase with friends, coworkers, or other people that you've met before. Don't use this phrase to talk about getting the chance to meet someone for the first time.
An "OK time" is a time when someone is able to speak with you. They're not busy, in a bad mood, on their way to somewhere, etc. Use this phrase at the beginning of a conversation to make sure that the other person will be able to speak with you:
A: Hey, is this an OK time?
B: Uh... I'm actually in the middle of something. Can I come by in, like, 10 minutes?
You can also say "a good time":
Did I catch you at a good time?