Double debit for voucher advance

I am writing to formally lodge a complaint regarding a double debit on my account for a voucher advance I took, and ongoing failure to resolve the issue. I reported the issue about a month ago and I was assured that the refund process was underway….despite multiple follow ups via phone and Vodapay support I still haven’t received my money back,each time I call I am told that the payment is “still being processed”. Most recently I was asked to provide my bank statement to support the claim which I promptly did.However, to date, there still no resolution or refund and I have received no updates.