Billing issue and Customer care ignoring me

In April I took out a LTE home router on a month to month package, at the time of sale I was told that I had to make a payment for April (rest of the month) and then for May upfront, I did so and received my router, at the end of April I received a statement saying I owe Around R 1700 which was strange as the package is only R699 and I already paid R1200 this was in fact incorrect and only R512.60 was deducted, I sent a email to customer care ( this needs to change to we dont give a F*** about the customer) as up to now I still have no feed back regarding this. on the 6/05 I received a mail requesting information which I provided and on the 7th I received a mail from Similo Cube requesting the very same information so I got a bit rude and frustrated. now MTN is ignoring me and I must say for not even being a customer for two hole months I am regretting my decision for going to MTN. I need to know why I have already paid around R1700 rand for a R699 per month package when I have not even been active for (Two months ) active for around 40 days now ???