Cancelled my account last year now they want to charge me R1600

I deactivated my account over a year ago! Now I’m getting SMSs saying “you’ve defaulted on your rain acc pay now” apparently I owe 3 months from last year. I phoned and the lady didn’t even sound like she’s from this country. She said that I owe for three months from last year and that the account was only deactivated February 2024. That does not make any sense.