DSMS is a breach of contract

DSMS is killing my network speed and also my network stability. I am paying for an All-inclusive 4mbps Business DSL line via Afrihost. For the past few months, all was fine, my line was syncing at 4MBPS. I work from a home office, so I need the 4MBPS line in order to get a decent connection to my work VPN. However, yesterday, my line suddenly became problematic....I called Afrihost, and they reset the port, but now, my line only syncs at 2MBPS. I was informed that this is due to Telkom's new DSMS system which automatically syncs to the most stable line speed. <br> My understanding is that ADSL is supposed to be a best effort service. For the past three months, my line speed was perfect, running at 4MBPS, now, Telkom implements new technology and I am only getting 2MBPS. This is not best effort. I know that 4MBPS is working fine, so why is Telkom limiting my speed now? Who can I take this up with because I see this as a breach of contract by Telkom. They are obviously not offering me the best service (that I am paying for) i.e. the 4MBPS line (which was proven to be working fine prior to the DSMS implementation). I am unable to work from home and this is costing me money. Please revert.