just use the web callback you can use that anywhere any time. Personally i am in a similar place with a lot of credit on my account due to there stuff ups and i use web callback to make calls where ever i am.
I don't know the names of the apps as i don't use them but i have then them listed before both on this group and on
whirlpool.net.au. there are voip apps, calling card apps that work with smartdial and there may be an sms app but i am not sure on that one.
IF you want a refund talk to pennytel support. If they wont give it to you then just tell them you will take it up with the TIO. I got most of my credit back but still have $30 on my pennytel account but got over $70 back. Watch it when you leave them make sure you remove any cards etc as they start billing you huge amounts when you move your sim from them and then you have to fight to get it refunded to your card not your account.
I am with TPG now as i have Internet with them. $!4=15 a month gets me a 1gig of data, $300 of calls, and text and $300 to other TPG users. Pennytel for sim and data was $20 plus $5 calling plan plus call costs meant it was close to $30-40 a month. for me $15 is much better but i mostly use data and not too many calls. Depends on your usage.
If you have reception i think the new pennytel may not be bad as i think you will find it is all direct calls over mobile network not smartdial etc but not sure.
There are a heap of good deals for mobiles out there now it all depends on what you want and where you want to call.
Chris