Telkom pre paid

Been using Telkom for years now( on prepaid data) and never really had a problem until now when I get data which is supposed to last for 61 days instead it lasts for 30 days. I buy airtime and convert to data for the amount and data I need, now I have enough data to last for over a month but to my suprise my data has expired and it's only been a month not 61 days as they said. Never noticed this before which means they probably have been lying to me for years now.