I had about the same problem with my MACH as well. The merchant swiped three times and I didn't have any SMS alert.

I knew it went through the first time but the shop said no, tried second time only noticed the machine was out of receipt rolls and third time only had paper came out.

She assured me only one transaction went through. The fact is three went through after my CC application agent helped me to check my unbilled transaction. At that time, I had issue applying an online account as well.

Anyway since transactions went through, I had to go back to the shop to request for refund. I had the printing of the transaction as proof.
Fortunately for me, the boss was damn nice and she knew my card was charged three times when she closed her transactions that night. In fact, she has prepared the money for me and waiting for me to collect the money from her.

She was saying she didn't know how to contact me because she didn't have my details and she knew I'll be back.

Thanks for the useful info. I will keep the receipt and in case anything, I will go back to the shop.