UNAVAILABLE CREDIT BALANCE

Good day , Due to lockdown I was not able to make in-store payments , and opted to make EFT payments directly . Total of R 600.00 was paid for the months of April and May , and no purchases were made on the account during this period . Today , upon query , the in-store clerk advised me that the only available credit on my account is R 64.00 . I wish to query this as it seems faulty . Please advise Urgently .