The question is vague and lacks any specific details. It could be taken to mean, 'How do I listen to phone conversations?' in which case the answer is that you can either simply have a phone conversation - by picking up a phone when it rings and talking to the person calling, or by calling a registered phone number by phone - or by recording a conversation using a function of certain phone handsets. All phone companies also record conversations for legal purposes. If the question means, 'Should I listen in to other people's phone conversations?' then it is demanding a moral answer, that is, is it morally right for me to listen to another person's phone conversation? From this point of view there is no easy answer, as the nature of morality makes any definite answers difficult, if not downright impossible. There is an ongoing philosophical debate over whether or not morality should rightly be considered to be absolute or not, that is whether it applies the same to all possible situations, for example: Listening to phone conversations which you are not a part of is always wrong because it is interfering with another person's privacy; or whether morality can be affected by circumstances and is therefore subjective , for example: Listening to another person's conversation is usually wrong , but right if you have that person's permission. Essentially, the question from a moral standpoint comes down to a dispute of rights. For by listening to another person's conversation you are interfering with their rights to privacy. This can be considered wrong, and so you should not do it, because as individual beings with rights to liberty, equality, etc. We can take for granted the right to privacy. However, inevitably the circumstances of the situation are going to affect your decision to listen to a phone conversation or not. That is undoubtedly it's possible to imagine scenarios where it is better to listen to a phone conversation, this is because otherwise you would be breaking a larger moral duty, for instance if you were a government appointed security officer it would be acceptable for you to listen in on a drug dealers conversation if it allowed you to stop a drug dealing ring which was causing harm to the people it sold drugs to. Here your obligation as a member of a security service overrides your duty to respect the drug dealer's privacy rights. However, it's clear that since this is otherwise open to abuse, your obligation cannot be seen as totally overriding your general moral duties as a human being, e.g. Just because you a police officer doesn't give you the right to listen to any phone conversation you like. That's why it's important that the state is so structured to prevent abuses of power, for example by ensuring phone taps can only be used with a judge's express permission. In ordinary life this same dispute between moral obligations and your duty to protect privacy should be considered.
