Trying to rip me off

I am a new customer with mweb-I have to use adsl because there is no reception in the area.Their service was good and quick(ie delivery of router).<br> My problems started with the 2nd account I got for approx R750.I had requested a deal where I get 5 gig for aprox.R450.I phoned them up ad was eventually put through to a manager(Janet),When I asked why the account was R750 there were quite a few explanations all sounding very good-basically saying I had gone over the 5 gig and was being charged .20 cents per meg thereafter and that they had cut me off at 8gig which was my credit limi of R500?My credit limit !?My arrangement was for 5gig there was no discussion of a credit limit as I would only be using 5 gig and no more.There was no notification of me reaching my 5gig limit-I was told that was because it was in the middle of a session.When I was with Telkom when I reached my limit I was cut off and would then have to prepay.The manager started talking about hard cap and soft caps and said she doubted if they could cut me off at 5gig(it would be bad for the bank anyway).I have not received any contract(only a delivery letter for the router) and I definitely did not agree to a credit lim