expiring my data which is only suppose to expire the 22 JAN 2020

Hi there to whom it may conern. I understand that my data bundle only last for 30 days when i do a top up, right. BUT here is the thing i received a reminder that my data will expires on the 22 Dec that is what i read quickly (expires on the 28-12) so what i did i did a topup for R149 on the 22 Dec that will give me a month data, now im sitting with 1024.00MB that is going to expire on the 2019-12-28. so whats up with that isnt it suppose to expire on the 22 Jan. So i paid for nothing R149. which i think is braking your T&C