Breach of Contract

Once again. MTN not living up to their promises. I upgraded my data package to a 7GB (5GB + 2GB) daytime data and 10GB night time data for R239/month in mid August. I have been charged R311.70/month and only received 5GB night data. I visited one branch was referred back to the branch where I upgraded and was told I had to phone the contact centre myself. I attempted this and was told the.problem was escalated then messaged 2 days later to say it was resolved - nonsense. I phoned again to eventually be told, after a very long conversation when I was first told that the reference no. I gave didn't exist, that I wasn't on the contract I said I was on. I was then told I had to get the contract and take it to the branch. Fortunately I had been emailed the contract to complete before I finalised it. I took this to the branch. Again a long drawn out discussion. This time I was told it was a Saturday and only during the week could enquiries be made to the accounts dept. An email had been sent 6 days before to the accounts dept by the branch who had not followed it up. I was assured the sales person would follow up and contact me on the Monday. Nothing. I phoned Tuesday - sales person and branch manager on training. I was contacted Tuesday afternoon and assured the problem would be sorted by Friday morning latest and that I would be refunded the extra charges. By Friday afternoon I now had 5GB + 2GB day data. I am trusting the extra amount deducted will be refunded or credited. As yet night data has not changed from 5GB to 10GB despite promises that this will be done. I have lost 6GB of day data since upgrading and had to purchase 1GB for R149 to access my emails, I was overcharged and also I have lost out on 15GB night data since signing the contract with no sign of this being rectified. This is unacceptable. What now? A pity that MTN is the only data I can access in my area - I would otherwise definitely change to another service provider.