MTN Momo flop

In the 15th and 16th of March 2021 I bought food vouchers via the MTN Momo app the proceeded to the store on Tuesday the 16th, when I tried paying using the vouchers they were denied because of an issue with the date. I called the Momo call centre as soon as I got home and I couldn't get assistance because if loadshedding and u could only talk to an agent the on Thursday who said I would get feedback the following day till today nothing.i called them again the following week and again was told I'd get a response by the filling day,nothing came so I emailed them the required information and was told I'd get a response within 3 working days, well I've since emailed them 2 more times and still no response. I don't want their vouchers anymore I just need them to refund me so that I can terminate our relationship because they are not honest and.they have no sense of customer service. I'm highly disappointed.