RE: BREACH OF CONTRACT

I took a contract with Telkom via Sell Direct, a 2017 Huawei P8 for 150 monthly. Telephonically, it was agreed that the monthly installment would be 150 (This was emphasized). Shockingly, an amount of R170 is being deducted monthly instead of the agreed R150. I called Telkom asking for clarity / assistance and I was told that they can't help me, I have to call Sell Direct on ********** 500. I have been calling them for the past 6 weeks, the phone rings and hangs up ultimately. Kindly assist ****b - **********