Vodacom still billing me 4 months after switching to MTN

I live and work in Underberg KZN. (relocated from PMB June 2017) I have been a vodacom customer for 10 years. I had to switch to MTN due to the poor vodacom signal in Underberg. I switched on the 30th of August 2018. MTN said they would cancel my Vodacom month to month contract because it was more than 2 years old. On the 1st of September i was billed by Vodacom. I phoned customer care and they guaranteed me that my contract will be cancelled. On the 1st of October i was billed by Vodacom again. On the 1st of November i was billed by Vodacom again. On the 1st of December i was billed by Vodacom again. Vodacom changed my cell number from ********** 137 to ********** 964 and are carrying on billing me. Vodacom please sort this out. Vodacom owes me R1450.32 (R362.58 x 4)