Is it permissible to work in transcribing and translating recorded phone calls, and what is the ruling on the earnings acquired therefrom, given the doubt about their legality or uses? And is this considered espionage? What about the earnings from previous work that have not yet been paid?

The Sharia (definition) prohibits spying on people's private lives and disclosing them. Phone calls are considered private, and thus, spying on them and recording them is an act of betrayal and a forbidden transgression. It is not permissible to work in phone call translation unless it is confirmed that the speakers are aware of it; otherwise, this would be an endorsement of espionage. As for earnings acquired before knowing of the prohibition, there is no harm in them. Whatever has not yet been received should be given away as charity.