Contract upgrade hidden extension period

I requested an upgrade to Premium, with only 8 months left on my current subscription to Compact Plus I thought it would upgrade my current contract but keep the term the same. Since the voice navigated options did not give any specifics, I thought to speak to an agent after the upgrade to confirm the term. To my surprise thecontract has been extended to 24 months without it being specifically stated. On requesting to revert to my old contract, I was informed that I have to pay R180 penalty fee. This can not be legal since all contracts have a cool-off period and this was literally minutes after doing the upgrade. I escalated to the team lead but the answer stayed the same. This cannot be acceptable or legal even.