You can use Pingo's PINpass feature to avoid the need to send your account number and PIN.
Calling cards are rarely a good value -- you can usually get lower latency and better quality, at the same or lower cost, by using a VoIP provider directly from your OBi. Also, most of those providers do not have any monthly or other surcharges.
Which countries are you calling with Pingo? Landlines or cellular? Approximate monthly minutes usage?