MTN contracts are a ****

I regret taking a contract with MTN I closed my cellphone contract within months and I was given amount to pay I paid two separate amounts and I after few days I was told by them that I paid extra by R8000 I have been writing emails to them with no luck,then last month I got invoice that I owe about R400 from my previous account l.They using the number I was using for the contract 🥹🥹