MTN disappoints

I have been a loyal MTN customer for many years and also trained some their staff a few years ago. My monthly bill for 2 cell phones, 2 computers and a tablet averages R2 500 per month. 2 months ago I added a third computer, all on contract.<br> <br> Last month I received a SMS my services is suspended due to reaching the credit limit, went to branch to find out on what instrument, was told it was data charges on 3G card, so stopped using it and paid R3000 in. This month R9819,85 was just deducted from my banking account. I went to branch again where a very rude staff member (name available) told me it was my cellphone (capped and I load data when finished....?????)<br> <br> My questions:<br> 1. When does credit limit apply and when not?<br> 2. Why did one say it was my 3G card, the other one says it is my phone? (Had my phone for nearly a year and nothing changed, only a new technology SIM card issued by MTN and I asked, at no additional cost?<br> 3. Could staff please be trained that it is their job to assist?<br> 4. Received a sms: Your service provider made changes to your usage limit and therefore can your account not incur any out of bundle costs???? Without any consultation?