Failure to refund me after taking the payment twice.

Good day, I would like to place a complaint on my experience with pnp as I went there shopping on the 22nd of October 2020 and they made me twice the amount I was meant to pay and when I went there to request a refund they said they couldn't help me and now I have spent even more on airtime trying to call the head offices. Proof that supports this statement is readily available but they still couldn't pay me back my money, I must say I am really disappointed in their service.