Data ********

The package I am signed up on gives me 650MB data per month. I received an sms this morning stating that my package now gives me 500MB data per month. I called into Vodacom customer care and they tell me that it must have been a system error sms (but cannot confirm this). Can vodacom just amend data without telling their customers and keep their subscription rates the same? The service from Vodacom is becoming worse and worse each year.