Discovery thinks they can take us for a ride

After being retrenched I was looking for medical aid I could afford until I get a job. I checked discovery and their brochure had key care plus on R290 for the lowest income band which I am on since I'm unemployed. I called the call centre in December they confirmed that it would be R290 for myself and R290 for my child which brought it to R580, they lady advised that I needed to send them a bank statement or I would be debited a higher amount. I couldn't do this over December so I made peace with a higher debit and than planned on sending them the documents so my February debit would be correct. To my surprise I call today to request the email address I need to send it to and the consultant tells me I can not pay R580 as this is ***** and I need to pay R1133. *****? A quote discovery gave me and based on it added me to the medical aid. To my understanding the call I made where I agreed to your terms and conditions is a contract so why are you not honouring the contract? Mind you before losing my job I was a client for 5 years. What a disgrace! Honour the contract I don't want your apology