This is an obvious scam.
As far as i can tell, there were no double spends. And on their site they clearly state this:
Refund?
If your transaction is not confirmed after 12 hours, we will provide you full refund within a day. This policy is not applicable to the tx which are removed or double-spent during the acceleration process.
So them saying no refunds is extremely fishy and seem to be trying to take advantage of you. They also say on their site that confirmation time for fees under $0.5 can take up to 4-5 hours and it's obviously been way longer than that.
They have no confirmed partners as well, for the record.