account from nashua mobile - vodacom confusion

I have been a loyal Vodacom customer for over 10yrs and have been disgusted with the service I have received over the past two yrs. I upgraded two yrs ago on a R135 top up. My understanding was that is all I would pay but only to discover a year later that I have been paying R250 because they all of a sudden excluded the device and BIS from the price which is not the way it was advertised. I went to enquire and they told me I misunderstood and that that was the contract I signed. I left it and continued paying my account. January 2015 I noticed Vodacom double debiting my account and enquired about it as I noticed R179 going from my account. When I called customer care they knew nothing about it. I was told to contact the bank. The bank confirmed it to be vodacom and because vodacom knew nothing about it I stopped the debit. When I went to enquire about a laptop I was told I can't because I have an overdue account that has been handed over. I have been up and down to no avail. I went to them after paying what they say I owe and now I found I have a bad name based on their mistake. It seems like the companies only choose to assist when they are approached by you.