Mango Airlines

I have booked 2 tickets from OR Tambo to Cape Town in 2020 just before Lockdown. My friend and I were supposed to go for a cruise. Everything was stopped because of Covid. I have requested a refund but was sent 2 vouchers which are expiring in April this year. Now I have booked an accommodation for a weekend, wanting to use those vouchers,guess what, mango is not available unti further notice. I tried to call even their Head office ***)no answer. On their website it states that they only refund if they are the ones who have canceled. All their phones and emails are not working.