iPhones lack the feature of call recording by default as a result of privacy law restrictions, therefore if you want to record a call on an iPhone, you will need to find a way such as utilizing a call recording application (through three, way calling), using a VoIP service such as Google Voice, or recording the call on another device through speaker mode, the only thing that you have to keep in mind is to check if call recording is legal in your area before doing so.