Mostly improvements needed

Positive is the small app size on your phone.
Negative it is just in Spanish for iOS. Additional codecs, especially for better quality, are costly.
It doesnt ring if someone calls me, only if the app is open. The design and UI could be more modern for iOS. No in-app explanation of basic features and tips for handling.

Ra-Orkon about Zoiper Lite voip soft phone, v3.6