20 Calls per day?

I bought ? new prepaid sim from Vodacom and received my number as per normal. I only found out on the Monday that the number belonged to aThabo somebody who deserted this number as he owed kjust about every clothing company money. The company who operate the one call centre Jabu connect does not pay any attention to my explanation and you can never get a supervisor on the line. Even phoning in and hoping to speak to somebody with brsins proved fruitless. I have put a block on yheir number on my phone but they still phone up to 30 times a day. This is getting a bit much. What can I do?