False advertising / Data throttling

I normally buy the 1.2GB Data bundle valid for an hour. However lately at certain times, evenings, most certainly weekends, public holidays and school holidays I am only able to use 500mb - 700mb max of the bundle before the hour expires. This has been happening so much lately. 12-15 times in the past while. I am very unhappy because this is not honest. The connection is being throttled and I am being charged for, but cannot download the 1.2gb as advertised. I also cannot get through to customer support. Only machines. I have been with Vodacom since cellphone were introduced into SA about 25 years ago. However this data throttling / false advertising / *****ing my money is quickly eroding all and if any confidence I had left in Vodacom.