Is establishing a call center project in a non-Muslim country, where the majority of clients are non-Muslims and calls may be used for matters that violate Sharia or occur between non-mahram individuals of opposite sexes, considered a permissible source of livelihood for a Muslim, taking into account that some calls may be for maintaining kinship ties or necessities?

Public phones are generally used for practical matters or to check on family. If it becomes known that someone is using the center's phone for unlawful speech, they must be prevented, due to the Almighty's saying: "You are the best nation produced for mankind. You enjoin what is right and forbid what is wrong," and His saying: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression." Therefore, there is no objection to establishing the center as long as the prevailing assumption is that it will not be used for unlawful purposes, while enjoining what is right and forbidding what is wrong to the best of one's ability.