paid bill still shows balance outstanding

I moved telecom provider in April, from Virgin to Zen. The final bill from VM dated 28th April, for £21.86 was paid to VM, by direct debit on the 20th May 2025. 

However, VM then issued another bill for £21.86 on the 13th May for payment due on 6th June, after complaining about this bill, the money was not taken but still shows as an outstanding amount on my now closed account. My worry is that sometime in future VM are going to turn up and say this second amount is still outstanding, despite the fact that it was paid. 

I want someone at VM to take ownership of this problem and delete the (not) outstanding bill from my account, I can then cancel the dormant direct debit mandate from my bank.

Regards