********** Bill of R 17 000 and noone will respond

I was in NYC in December. I realised I had left mobile roaming on for half a day. I realised my mistake and paid in the huge amount of R 4000. I was vigilant thereafter. Midmonth January, I received a bill for R 17 000. R 4 000 re-charged and R 6 000 for one four hour phone call when I was on a flight with my phone switched off - for which I have proof. Another R 3 000 for occasional roaming calls registering my phone number, not numbers I called. I have lodged 4 complaints in person