Is it permissible for a gold shop owner to purchase from wholesale traders by agreeing on the price over the phone, such that the merchandise is displayed to the buyer, then the price is transferred via bank, and the trader sends the gold to him?

It is a condition for the sale of gold with banknotes that there be mutual possession, meaning the buyer takes possession of the gold and the seller takes possession of the price in the contract session. It is not permissible to depart before this occurs. This contract is not permissible due to delaying the possession of the two counter-values, and it is called prohibited riba an-nasi'ah (usury of delay). The sale should be resumed when the price is available, with whatever they agree upon, hand in hand.