Tinkle Free VoIP is a free iPhone calling app which lets you make (free) national or international mobile VoIP calls directly from your iPhone. You can save on your Mobile Phone costs by simply installing the Tinkle and start making cheap calls. Phone calls between online Tinklers are all for free without any time-length/period limit. Any call with offline users or to PSTN landline numbers require tincoin. You can purchase tincoin in our Taobao store, online store or via IAP(appstore version only). USD and tincoin exhange rate is about 1:6.