Account handed over

I signed a top up contract with Vodacom in April 2017, having purchased 2 laptops, paying R249 each, with 500mb benefits each per month. I was over billed +R800 for May 2017, the initial month and +R5000 for June 2027. After 2 months and, with my credit score dropped due to their own internal error claiming I'm on open contract. It was ahassle to get through to relevant department. However I was credited. During the month of November and December after making all payments due I was not getting my 500mb on each laptop. After calling to get assistance they told me I owe R248 which h I have no comprehension as to where it comes from. I have not paid for January and February, and surprisingly Vodacom have handed my account over. I have been getting calls from this debt collectors making threats that they will list me on ITC. I recently receive a text from this third party stating: Vodacom settlement 7487.26 valid till 12h00 on 31/03/2018 to Symington&deKok, FNB, Acc: ********** 9635 Code:250655. Ref: VC ********** 3550 T ********** 511 F ********** 806