Not explain now I must pay

On 20 December 2017 I ran out of data. On the same day I migrated my 100 gig data contract to 200 gig and bought 200 gig once-off data. I asked the person if the once-off is going to expire the end off December. He said no. The 1st January my data is loaded. On 2 January I realized that the data use is my inclusive smartboardband data and not the once-off. The once-off will expire 19 Janaury 2018. I went into the Grove Telkom branch and asked if they can extend the expiring date on the once-off because I'm going to loose is. They said they could not help me, I must go to the TDS Menlyn branch. There they said they could not help me. I phone the call center only to hear the same thing, they could not help me. I asked advice and he said I must go back to the Grove branch so that the manager can escalate the data. I did that only to hear today according to terms and condition they cant do that. I payed R1049.00 for something I'm going to loose and it seems nobody care. When I migrate my account and when I bought the once-off data nobody explain to me that my anytime data is priority to the once-off.