switching the line

On many weekends my landline witch is a 4 meg line will stop.then start again,but then the speed is useless.after i log a call then i will be informed later in the week that my line is fixed.liked it happend about 2 weeks back.1 week later was the line fixed.this saterday the same again.line was fine,next moment it was useless again.the max down was from 30 to 50 kbs.when i called on 24.08.2015 about the line i was informend the i used to mutch data.THIS IS NOT THE FIRST TIME THIS HAPPEND.EVERY TIME THIS HAPPEN YOU CAN SEE A TECH WORKING ON THE TELKOM BOX.after that my line is ****,and my data is used.how can i upload 28gig on sunday with a speed of 50kbs.my complain is they are switching my line and some one els is using my data.i did complain about this many times but nobody did help me.