Been using fongo app for 5 years now, voice quality of phone calls is exceptional. Conversations are always smooth, no stuttering or delay in voices, way better than typical quality of a cellular phone call and as good as regular landline quality. Gets better and better with each update. I happily purchased the ad-free upgrade, thats how much I like fongo! My only gripe is Im still getting anonymous fax spam even though Ive got the Block Anonymous Calls setting turned on. When fongo fixes this ongoing issue app will get 5 stars.