I have the smarttalk app installed on both mine & my wifes & iPhone 5, both are linked via seperate BTID's to our landline account, so all should work ok, there is no blocking of calls etc.
From either phone we can ring landline numbers ok but calls to other mobiles are immediately disconnected when the receiving mobile answers, on the calling mobile you a get a "poor internet connection" message, from here I am unable to close down the call using the red hang-up phone icon, the call timer keeps incrementing - the only way I can shutdown the disconnected call is to use the iPhone swipe app function to totally close the app itself.
The internet connection is fine, as I say calls to landlines which is also WIFI work ok, so it is just mobiles. Looking at my account the only calls I am barring are premium or international calls - again mobiles should work.
I found this link and it partly fixed the issue, from both iPhones we can now ring other mobiles ok, however if we try to ring each others mobile we get the same disconnected call & poor internet connection message? so still some issue here, are phones (upto 5) linked to the same calling plan allowed to ring each other.
My joy was short lived, I can still make calls to landline numbers with no issues, but try any mobile and you just get disconnected as soon as the other end answers, the message I see is about a poor internet connection yet i can ring a landline from the same spot (my home 70mb BB) without a problem - THIS IS VERY FRUSTRATING - by the way I am using an iphone 5.
The Smarttalk app will be going into the list of apps to never be used again/deleted very soon.