Cool Ideas/Vumatel

I have been a subscriber to Cool Ideas/Vumatel for at least five years. I have a 1GB Fibre connection (the best you can get from Cool Ideas) but it becomes useless in the evenings. Cool Ideas says that it is working perfectly - and it is during the day- but at night, from about 7:30pm it becomes intermittent and loses the signal so that you have to reboot the program you are looking at. This happens every few moments so it becomes impossible to watch the program. I have complained to Cool Ideas many times and they always refer it to Vumatel who come back and says the line is working perfectly. My thought is that someone at Vumatel is using the line for downloading large volumes of documents/games during this time and that is why our line becomes intermittent. It could also be that the international link becomes saturated due to football or similar as it is usually at the time that the British games begin. This is not what I am paying for. I want a line that works all the time and that is why I bought the 1GB option. As there are no other providers where I live but Vumatel I have a big problem.