Telkom is disappointing- inflating bills

I have a problem with telkom. I took a contract (data LTE) in 2017 August. The guys from telkom came to my workplace marketing the product. They had pamphlets advertising the "special". Myself and a colleague signed up this contract that stated the following: every month you pay R199 and get 20GB, 10 at night and 10 during the day. I personally asked what happens if the data finishes, they said you will not have data until the next month, they further explained that, if you do not use all your data for a particular month you forfiet it. We got interested and signed up for this contract. The router was delivered for both of us at work and we started using it. Telkom continuosly deducted more money from my account and not R199 as per agreement, and whenever I try to resolve the matter it becomes a nightmare for me as I would not be assisted at their shops instead always referred to a call centre (081180) and whenever i try call i will hold for 10- 20 minutes until i give up. Now telkom says my bill is R1900,00 again i started calling, this time I managed to get through and I was told my account is on "spend limit". I told them that, i was never told about the spend limit, i dont even know what it is and I explained to them that even my colleague is still paying the R199 we were both told about and agreed upon. They said i must pay it as i have used the data.