Vodacom doesn't provide the service I pay for but expects payment

I have been a customer of Vodacom Fibre for over 2 years and I am sad to report the *********** abilities of this company. 3 weeks ago they cut my line speed from 30MB/s to 10MB/s and as a business I cannot connect to my clients with this connection speed. I have been phoning for 3 weeks and the problem hasn't been fixed and they still expect me to pay them. They have escalated the problem and that means nothing either because its been escalated at least 3 times with no repairs or communication with me. They JUST CANNOT FIX THE PROBLEM. I asked to cancel the line and they say I must pay a cancellation fee. Again, why should I pay if Vodacom CANNOT PROVIDE THE SERVICE I'VE PAID FOR? Maybe a Hellopeter review will help but I highly doubt it.