Bad customer service

I had a 24-month contract with MTN for a home router, which ended in June last year. Before the contract expired, I called MTN and also sent an email, as advised by the store (since they don't handle cancellations directly), informing them that I would not be renewing the contract and requesting that they close the account.

To my surprise, the account was not closed, and now I'm receiving calls from Saya Recoveries claiming that I owe money and need to make payment arrangements before MTN will close my account. I have refused to confirm my details with Saya Recoveries, as I believe I shouldn't have to pay anything since I instructed MTN to close the account.

I've tried following up with MTN multiple times to understand why my account remains open. However, each time, they either hang up before I finish providing my ID number or place me on hold for over 30 minutes, forcing me to hang up out of frustration.

In my initial email to MTN before the contract expired, I made it clear that I wanted the account closed. When I followed up on the same email recently and mentioned I would expose them publicly, they finally responded, saying I should have called before the contract ended. I then asked why they ignored my first email but responded to the second one only after I threatened them. I cannot afford to pay for something that should have been canceled when the contract expired.