The Glu credit system is broken in Heroes of Destiny
I have submitted multiple tickets on this issue and have not received any helpful responses from the Glu support team. There is a serious bug in this game that needs to be resolved. If my issue isn't resolved in a timely fashion I plan on contacting Google Play to try to get them to remove this app altogether until it is fixed. I will start an online petition and leave the details in a later post.