Billing trying to **** me for a bill I don't owe

I had a rain 4g sim card with rain years ago which was prepaid.No I see on my profile they say I owe them R1910 it's been months I have been trying to find out what the amount for and to date rain has no answers.Even whose they can't even access my billing account to see what that amount is for..They have never called or even provided any feedback it's 4 months now