I am being ****med

My contract ended in August 2019 and I cancelled my membership. I received confirmation of the cancellation in February 2020 with reference PF***. However in January of this I received an email from Landau attorney's claiming that I owe you 16000 and some odd rands. I forwarded the email confirming that my contract with you has been cancelled. I did not get a response from them after sending then the email. Today again I received a phone call from some lady claiming that I owe you money. Even if I had not cancelled the contract, there is no way I would owe you R16000. Why am I getting these emails and phone calls?