Fee Increase and pathetic customer service

"Hypa Fast Unlimited WiFi" My 75 year old grandmother signed up for wifi from Hypa 3 months ago and she's had two fee increases. When she signed up in March, the fee was R299 In April, the annual fee increase happened and the fee became R349. Now in May, the latest invoice is for R521. I've sent 4 emails or so, no reply except the automatic reply. When I call the customer service center, the line stays on hold. I've contact three departments: *** *** *** And nobody can clarify the fee increase.