Unprofessional , threats

A lady named Betsie from this company send me threatening emails, forcing me to pay more than what I can afford. She claims one of my accounts have been handed over to them for collection, yet I am still waiting for the mandate letter to prove this. I confirmed how much I will pay and she responded, yet today I got an email threatening me with legal actions, saying I made a commitment to pay the full outstanding balance, which is untrue.