Rain data services

Rain, for the first time in 2 years since I used they're services of unlimited data of R479 monthly decided to debit an amount of R 1700 of which they cannot explain they're reasons for debiting such an amount without my consent or awareness. No contract of agreement between rain and myself have ever been signed for giving them permission to debit money from my account without my consent. The worst part of it all is the fact that I haven't been using they're services for the past 3 months as I lost my rain data sim and normally you'd only pay when using their services. I urge everyone who's thinking of ever going for their services to be aware of how they operate as it is really unpleasant and dishonest. Upon contacting them regarding this wrong billing, an email was sent saying the remaining balance of R600 will be used to pay for this month's services whether I was using their services or not.