Contract upgrade monthly amount higher than contract signing

I am over 15 years at vodacom and this is my first serious complaint. I upgrade my existing contract at Garden Route mall at end of 2017. for R170 per month because i dont want it to be high , because i budget for my other contracts also. When my first invoice of R340 come they told me the cheap device i took was also R170 + R170 with my contract . I said no i sign just for a monthly contract of R170 and nothing more. Vodacom freeze my account and make it pay as you go. A few months later my bill is R2800. I tried the customer care a few times explain everything and said where is my benefits every month since i didnt get any minutes or data. They said they will sort it out and now my contract is suspended. Very poor service and i am tired of customer care because it seems they didnt care. I am wiling to pay it up to date if vodacom sort there problem out + i want all the outstanding free minutes for the months my phone was suspended otherwise leave everything and make my number prepaid . i am tired of all the false promises to sort it out. I am a loyal client and my whole family use vodacom.

Kind Regards