Cell C missing out important details

I have recently requested a settlement statement letter from Cell C, they did provide with one and the payment was made and proof submitted, they also even sent me a paid up letter stating that the account has been closed( 16/06/2018). today i received a call from a lawyers office claiming i owe them money through cell c, this is extremely upsetting in the sense as why would they not include of advice me of the account been dealt with by a lawyer and included the fees in the payment, this is very misleading and unprofessional and proves that cell c does not provide valid or correct information to clients.