Pathetic service from Vodacom

I have been paying the same amount on my vodacom contract for 18 months. Suddenly this month I have been charged extra. I have tried contacting them numerous times on 082 135 but I either get told call volumes are high and get cut off or put to self help options! Now with no other way to contact them I am left to waste my time daily trying to contact them as there is no other method of contact!! Pathetic service from such a large company!!!