Retel quality is not bad. Their free calls:
1. Free trial of 3 minutes before u register,
2. Free Rebtel APP to Rebtel APP calls.
They used to offer free call, some funny call-back, but it may have been stopped ~2 weeks ago.
Check today, US$1.9 cents/min., seems like the paid $1 get $5 promotion may still be on.
Another company which could be "possible" -> Tel3.com by Justdial.ca. US$0.8/min for 6 months, then $1.3 cents/min after. Current promotion of paid $10 get $10 extra, plus 50% bonus credit for calls on Mothers day. Use promotional code "MOM16" and 309355. Quality should be OK as Justdial/Tel3 has been around for many years.
Above is not my code, just copied from the web. Have fun!