H&M customer services don't respond

I purchased an item not too long ago from H&M waterfront. A few minutes after i left from the mall, i realised my debit card was missing. I remembered that H&M was the last store i had purchased an item in and that the cashier may not have handed my debit card back. After several times of calling their landlines, none were responded to.
I am thus extremely disappointed in the customer services rendered.
In future i would like that h&m sort out their customer services line in case of emergencies.
Thank you