Misleading add to open an account

There was an add which states if one opens an account before the 27th February 2022 and approved you will receive a R500.00 voucher. I opened the account and got approved as per the add. I then did a follow up on the voucher and got a e mail response stating that it will be loaded on my app on/after Wed. On the second Wed since i have not received the voucher, i did a follow and till this day have not received any further response. I have now requested that they cancel my account and i will only pay for what i have used. I not responsible for their initiation fee as their add had mislead me.