Sixty60 app unreliable

I used the Sixty60 app this morning, made the payment, and the app just cancelled the order. I have been calling the store in Bonearo multiple times but they keep telling me to wait for a callback. All I need is proof of cancellation so my bank can reverse the funds. They are not taking the matter seriously and this is my grocery money. The call center's are not working. I have no idea how I'm going to get my money back. Utterly disappointed.