(私は日本語が下手、ごめんなさい) The mobile phone call price in Japan is serious high. To saving money. My solution is use a 050 number (SIP in Japan) and a SIP client on iPhone. Ive confirmed that Acrobits supports iOS 10 CallKit which makes SIP calls very convenient. And Ive confirmed that Fusion-SMARTalk supports third-party SIP client.