I wouldnt recommend this text and call app just for the fact that it charges you credits to send and receive text messages. I understand that you have to pay for minutes because that is standard with the text and call apps. What is not standard is having to use credits for text messaging. It turns out to be very expensive and more logical to just buy unlimited text on your regular phone plan or go with another app such as text me or text free. Those both give you a new phone number that you can use for free texting and calls for a low price of lots of credits.
Maur_Mix about Dingtone: Phone Calls + Texts