Cryptocurrency exchange Coinbase (COIN +0.4%) is starting to test a subscription-based service that will include such benefits as zero-fee trading and prioritized phone support, The Block reports, citing materials it has reviewed. Called Coinbase (NASDAQ:COIN) One, it will initially be offered to a small number of users. It isn't clear how much it will charge for the service, the article said. "Coinbase has started testing a subscription product for our customers," a company spokesperson confirmed to The Block in a statement. "Customers in the test group will have the ability to buy, sell, and convert digital currencies on the Coinbase (COIN) platform without a Coinbase fee for each trade (spread fees still apply)." The future product will be shaped by the feedback Coinbase (COIN) gets from its users, the spokesperson said. That's part of the the firm's mission to diversify its revenue stream beyond its main trading operations. Coinbase (COIN)