Line speed

I received my vodacom order today, I ordered a 100mbps line, I have tested the unit, it seems I can only avarage 15mbps and below, is there a way of assisting in increasing the speed or is this the maximum I can get? When I check on your website my house is covered under the 100mbps range, the only one I don’t have is 5G, with this line I’m literally running on 15% and less of the maximum speed….but I have to admit, that the line is somewhat stable….no buffering as yet…