Paying for 4mbps service but lucky to get 1mbps

Still in process of resolving Telkom billing issue however since installing 4mbps line on 4 Sep 2015 and being charged for uncapped 4mbps ADSL service, I'm lucky if I get 1mbps service from them. Intermittent slow service, at times complete service failures, constant disconnections, it's extremely frustrating. Called service centre and Tweeting Telkom online, left message because they tried to call me using hidden numbers which I don't answer. Asked them to call using normal line and they ignored my request - play fair Telkom!! After telling me that they tried contacting me and there's nothing wrong with line,the case is therefore closed. After showing regular speed tests and service failures on Twitter to them, they asked me to \flush DNS via command prompt: ipconfig/flushdns then enter & reset router & try again". Propellerheads aside"