apps for call/text
for calling use Bobsled Calling... its a REALLY GOOD APP... by the way, I use the Samsung Galaxy Player 4.0 US Version and it works good for me.
and for texting... just use TextPlus, there's nothing bad in it, but its only good use for you if you want to text to US/Canada.
I heard Whatsapp Messenger is good too.. but its not compatible with my device.
Anyhow, I used to use GrooveIP but stopped because the quality is bad.
Hope I helped!