Vodacom - what a lying bunch of people

What a bunch of lying people working there. They phone you to give you a better deal and suddenly when you get your debit order it went up from R600 to over R900 WITHOUT my permission and no 14 days document was forwarded should I want to cancel. Just because you are forced to deduct via debit order doesnt give them the right to chop and change as they like. Now it is more than 14 days later and I must sit with a monthly account of nearly R1 000 and if you dont pay, you get blacklisted.