Make your own callback service. (2 Voip accounts [Betamax I suggest with sip access]) + a free DID number + 2 more things (Search for tutorial)).
Simply you will just call your free number and hung up and then it will use you1st voip account (I assume betamax will do it free of charge) and call you through your 2nd voip account (Also free of charge to US).

Again, here what happens:
1- you call your number and hangup (This won't cost you anything)
2- you will be called with your 1st voip account (Make sure you can receive your calls for free)
3- You will dial your number + # on end
4- You will be calling number through your 2nd voip account
5- Enjoy talking

This will costs you near $0 and you don't need any internet access (No need for plan).