Hi @Emma-And-Jon0,
Explain them about your minimum stay policy for July, and if the don't want to adhere to the exsiting policy, request them once again to cancel on their own.
If they still refuse, keep it as it is, don't do anything from your side, it'll end up as a no-show and you won't be penalised. If they write a bad review, call to Airbnb using the number on the itinenary and explain that guest did not turn up yet wrote a negative review. Airbnb will delete it.
Make sure all your communication is via Airbnb.
Cheers,
Jeet