Bad business practice

I do online surveys and some pay in takealot vouchers which I have used in the past to buy airtime however now when I tried to buy airtime with my credit at takealot, which is my money paid to me for my time, I am informed I cannot buy airtime with money paid in as a voucher which I find totally stupid, bad business sense and practice, not allowing persons to buy what they want, such as airtime, and are adamant that no airtime can be purchases using credit from a voucher. This has made me feel very negative toward takealot and will not be using their services in the future and I will discourage others from doing so as well.