Slow or no internet

I have MWEB internet at home. Late afternoons or at night I am sitting with very slow or no internet at all. I get to the point were I need to use my Vodacom tablet to log into the Mweb webpage to log a query. I have logged the queries a few times without any help from mweb. But my payments have to be on time, yet I do not get the service I am paying for. When I do log a qeury for my problems at night, MWEB does a line test the next morning and tells me everything is fine. I was warned that if I use too much internet i will be capped or line speed reduced. Someone in my neighborhood is draining the speed of entire neighborhood, so I am asking what are you going to do to assist me as a paying customer