Telkom Internet Nightmare

Everything started about a month ago when we changed our line speed from 4mb to 10mb. It took about a day for the line speed to change from the 4mb to the 10mb , as Telkom said it would. When the modem showed the new 10mb line speed I ran a speed test and got around 8mbps, which is normal. Everything worked fine for about 2 hours and then our line speed slowed way down, to about 4.5mb. We logged a fault , Telkom could not find anything wrong on their side. A technician came to the house and tested everything and found that everything was working 100%. He said that the problem was definitely on Telkom's side. Now I thought that maybe we where being throttled , but when we went in to the Telkom store and they said no we where not being throttled. Still thinking that maybe we were being throttled I waited till the new month started , not downloading anything till then. Then I ran a new speed test on the 1st March 2015 , the speed was still 4.5mb . So anyway we logged another fault which is still unresolved ( REF no. ***9) . Today I checked our max line speed and now it seems that Telkom changed our 10mb line to 4mb sometime this week without our permission . What is going on?