I had a cellular phone contract with Autopage cell...

I had a cellular phone contract with Autopage cellular, never had problems with them, and know that GloCellSA took over lots. GloCellSA billed me R12948.48 on my debit order as I went to visit my brother in Australia as his son died. They said it was for data used! , I know my data was switched off and I used their WiFi every time I was on Internet or social media to my family at home. My itemised bill shows free usage then 16 sec later R1000 + then free again. so I paid R12948.48 because I'm no crook and will dispute it later, then 2 days later I received a call from a guy from GloCellSA, very threatening and agressive, I owe them R68000.00 and got 21 days or else! !!!! .......
I know I used WIFI and my data were switched off
Do not use GloCellSA and they do not reply to emails and send you information