Tim Hortons

On April 7 I used the Tim Hortons phone app for the first time, at the counter. It took my $16.47 out of my phone account but the clerk said payment did not go through at their end so I had to pay again with cash. The clerk said this happens frequently - so many other people are getting screwed out of their money as well. I have been communicating with Tim's since that time and they blatantly REFUSE to reimburse me. How is this legal? Tims sucks and they need to give me my money back and I don't want to hear any more of their BS excuses. They are wasting everyone's time, especially mine. I've already reported this to Pissed Consumer and BBB and I will get my money back one way or another. I'm just really shocked that for less than $20 Tim Hortons is fine with the bad publicity and formal complaints that could all go away if they just gave back what belongs to me.