Wifi with mweb is still not up to standard....

Did put a query in at mweb, but wifi and internet fibre with a 20mbps line do not allow me to watch a youtube video without buffering at least 10 times in less than 2 minutes. Dstv streaming buffer and netflix that require only 5mbps so what would you say is the problem? The service provider? Never had this problem. The only advice they give me is restart everything.