Poor service and empty promises

During 21 days lockdown ,I paid an amount of R500 electronically to Edgar's as a monthly instalment because the store was closed.Unfortunately,I put a wrong Reference number.In May ,i,ve send a proof of payment to Edgar's Head office,they confirmed and promise to update my Account.Since,then my Account was never updated..I always receive threatening calls from them that they will handover my account to their legal team.Now,I've received an Email on the 7th Aug 2020, that they are giving me 20 days to pay.Please ,help me