Telkom Mobile Over-charged

I took a telkom contract at istore last year May and it stipulated that my contract is R359 a month. I have been trying to contact telkom with no success. on the 26th of this month I called again because they debited R1400 on the 25th and another R1400 the following day. My concern is I do not even use the sim-card just the iphone6s. The consultant I spoke to said the matter is being investigated and that they will call in 2hours but they never did. I am tired of reversing because it affects my credit score.