Cell-C Min Data-charge now 25kb not 5kb!? (since 24th April...) - is this legal?

So, on top of the OOB data hike, there's another DATA cost hike that Cell-C seems to have slipped under the radar. Although there is no mention of it in the T&Cs, Cell-C has always charged a minimum amount against your 'data bundle' - so if you only use 1kb in a minute, it charges you for 5kb [FYI - I know vodacom's minimum is 1kb, but don't know the rest!]. However on 24th April 2014, this 5kb lower limit has shot up to 25kb.

If you login to Cell-C's my account page (http://www.cellc.co.za/my-account) and go to Call History Search [badly named I know!] you will see all the 'charges' made to your account. As you can see highlighted from my account - pictured below - I used 1.6kb on 23rd April - and Cell-C charged for 5kb of data against my bundle.
Just 5 hours later - on the 24th April, I used 1.7kb, and was charged for 25kb...


I've called Cell-C to ask about this, but no-one at customer services has a clue!

Anyone else been experiencing this? Did anyone get any notice, or read this 'hike' in their T&Cs?

Just looking at my data usage in the past month; this has increased my bill-able usage by around 5%.
Moreover, just looking at a different SIM, they've upped the 'minimum charge' for OOB data from R0.01 to R0.03. So if you're phone connects and only downloads 1kb, they're charging you R0.03 for that, or R30/mb!?

Is this even legal? Would love to hear from others...
Cheers,
Richard