Is it permissible for a person to buy a phone that was found by someone else, and its owner could not be found after attempts to search for him, and then it is sold to the buyer? And should he pay its current price or its original price as new?

Taking the phone and breaking the SIM card with the intention of not returning it is considered treachery. Whoever takes something with the intention of treachery, it is not permissible for him, and he is obligated to guarantee it to its owner, for the Prophet, peace and blessings be upon him, said: "The hand is responsible for what it has taken until it returns it."

It is not permissible to sell the phone because it is considered usurped. It must be taken back from whomever it was sold to, its price returned, and its owner sought. If it is impossible to reach him, its value must be given in charity for charitable causes on his behalf.