Discovery is sleeping at work again

I have received an email stating that I owe Discovery Health R6000.00. Reasons: Plan change, Dependent Withdraw & other.

I have changed my Plan (from Classic Saver to Essential Saver) in April 2019. It was effective from the first of April 2019. I have added a dependent on the 1st of January 2020 AND HAVE NOT WITHDRAWN HIM. Where do you come across such nonsense?

Does it take you one year to realize that there might have been a problem? Which I don't believe because when I moved from Classic to Essential I have paid the difference used from my day-to-day.

Nowhere have I signed or verbally confirmed that I have removed a dependent?

This is highly unprofessional from Discovery to come up with such nonsense.

Please resolve this issue ASAP. I will not be held responsible for any amount. I have paid everything.