Call recording is a great way to cover your backside. If you promised one thing and the customer expects something else, here is your proof. Recordings are also useful for training new customer service representatives or sales people. Record their calls and evaluate and educate them on how to do better. Or, if the call was perfect, use the call for training others.
There are some legal issues with recording calls. Some laws prohibit recording calls without the other person knowing it. Some laws require a "beep" tone every minute so that you know the call is still being recorded. Check your local laws before recording any call.
Call recording can be done in a couple of ways once you purchase a license. On the 3CX VoIP Phone software, there is a Record button. There is also a Record button on Snom phones. Both do the same thing, which is starting and stopping the recording of the calls.