Is it permissible to buy and sell gold by phone or other means of communication without actual physical possession, with payment completed by bank transfer or other means, and with mutual trust or periodic settlement of accounts?

It is a condition for selling gold for silver or currencies that possession be taken in the contract session. The proof for this is what came in the authentic hadiths that prohibit selling gold and silver on credit. Contracts made through modern communication methods are considered valid. So, if immediate possession of gold or what takes its place can be achieved through two agents, one for each of the contracting parties, during the call, then there is no harm in trading gold over the phone. Otherwise, it is not permissible.