Mowana- Bad service

So I got a voucher from a friend in 2017 /18 which was expiring in June/August 2020 . I used the voucher last year once and still had money left in the voucher, which I was going to use after the lockdown rules were eased.

Upon reaching level 1 of the lockdown, I called Mowana and they told me that the voucher was redeemed last year. I informed them that I only used part of the voucher and not the full amount and maybe the zero balance was due it the voucher having expired, But they infirmed me that , that was not an issue as they understand that we were still under lockdown.

I was communicating with a lady by the name of Michelle who, not only was annoyed by my phone calls but made it clear that she was not interested in assisting me. It has been over a month since I sent her a follow up email and have no response from Mowana.