Spark "Terminates" my children and withholds their report cards, even though my account has a credit balance!

I knew the Sparks Accounts department was inefficient, but today they took things to a whole new level.

They sent me a strangely-worded termination notice, claiming that they've been telling me on "numerous occasions" to settle my account. The problem is, my account actually has a credit balance!

For some context, there was a time about 3 or 4 months ago when my account was in arrears. That was because they had messed up my account with incorrect billing and I had to fight them to fix it over a period of close to a year. They finally resolved my issues and fixed the incorrect billing. Soon after they resolved my queries, they sent me a what was actually a first, but "final demand", as they called it. That's just about all the "numerous occasions" they've referred to in their termination letter. I then paid them way more than the outstanding amount, taking my balance to credit. I hoped I'd never have to speak to them again, but I was obviously wrong.

On Friday, 10 December, the last day of school I received the termination letter, telling me my children were being deregistered. I wish they'd sent this letter 3 months earlier so I'd have time to look for another school, or at least included in their letter how they'd be refunding me the amount I've already paid in advance.

Oh, and to top it off, they've withheld my children's reports, something I believe is *******, even if I'd actually owed them money. My kids were looking forward to receiving their reports but now they're devastated and I don't know what story to tell them.

PS:I tried my best to be as polite as possible, but I'm fuming!