3 Managers who just didnt want to listen

On the 17th November @ 19:55 I went to Ottery Hyper to get pampers for my baby. I had 3 vouchers to the value of R250 from proctor and Gamble to purchase pampers or any product that they produce. On the voucher states that i can purchase any 1 product or products that were listed on the voucher. The cashier just called the manager 1 to confirm that how to process it. The manager then read the voucher and said that i can only use one voucher per product and not the full R250 - which is the price of the pampers. She called 2 other managers who did not want to listen and insisted that pampers allows only one voucher per item. Nicci who was the last manager to approach me was so rude that I just walked away. I called the pampers call centre now and they said that they have never had this issue before because it does not stipulat anything like that on the voucher. i had to use my last money to buy another pack of nappies because 'managers' cannot read. Even the packer and cashier said they understood what was wriiten on the voucher and they cannot understand why their managers are not listening. I am upset because as managers we suppose to be more educated but clearly this is not so.