SARS refunds outstanding for past 5 years

Since 2019 SARS is sending letters statung that my bank details needs to be verified and they strivee to do so within 21 business days. So I guess in 5 years it has not been 21 business days? Each year I complete and submit my returns and each year the amount that SARS owes me keeps on climbing. I've been to the branch etc and still nothing. What must I do, SARS?