Is it OK to record phone calls?

Is it OK to record phone calls? What apps do you use for that?

I often record phone calls, since I found how to record a call on an iphone. It's convy. I like this app it helps to record important phone calls. With this app I'll never forget names, dates, or places that were mentioned during the call. Useful app today, I often have business calls but I do not have an opportunity to write down important details anymore.