Priority consumption of data

On 25th March my data was almost depleted so I purchased 10Gig bundle for R149.00 Towards the end April I checked my balance and found the 10 Gig anytime date had not been used although my included data for April (due to expire 1 May) was depleted and data due to expire 1 June was almost depleted. I contected Customer Care and queried the situation. The consultant escalated the query advising I would be contacted within 72 hours. I received a message to say my case was receiving attention and another saying it had been resolved. I checked and found that the top-up data was still not activated and I again contacted Customer Care who advised "that is how it works". It subsequently expired 2 days later and I was left high and dry. My understanding is that the top-up data should have kicked in before the April included data as it was purchase before the kick-in date.