Charged for a balance I had already paid in cash

On the 25th I was picked up by a gentleman by the name Zamukwaka,and my fare was R398,62 I paid cash and even gave him a R 50 tip.However that afternoon U er receipts said I paid R52 which I was sure was an error they would rectify and since it did not involve me I had already paid I did not think much of it.However a week later I’m being told I owe R398,62 I have reached out to uber and they said they would clear my account,as they are aware it was a systems error however it’s been over 2 weeks and they are ignoring my messages.I need my account to be cleared I have not used my uber app due to that outstanding fee which I am not willing to pay.