Letter of demand but I don't have a contract with Vodacom

Ordered a contract phone online last year. The wrong phone was delivered and Vodacom collected the phone within 3 business days. I complained on hello peter (link https://www.hellopeter.com/vodacom/reviews/this-is-not-what-i-asked-for-*** ) They apologized and assured me that I would not be charged for this but they actually did. The debit order went off and they've never returned my money back. Today I just received a letter of demand from Vodacom regarding this same phone for R1924.94 for what I don't know. I dont even know how to feel about Vodacom at this point