How can I record calls in my IPHONE

There is no way to do so built into iOS or the provided telephone app.

Best advice we can give is check your local laws regarding telephone recording and check the AppStore.

There are different laws for different countries, states, etc.

Some only require one person in the call be aware it’s recorded, some require both parties to be aware and consent.

In most locations, recording phone calls is illegal. Apple does NOT provide a way to do so, because it is against the law pretty much universally. We can't help you circumvent laws here.

You're welcome.