Vox unauthorised charge to my account

Cancelled service on 1Mar19. Suddenly get a charge to my account for a router for R1100. No call or communication. Turns out the new tenant has a deal with Vox and is using the router they have just charged me for!

After many emails to Vox I can't get a credit and now they say I didn't cancel my account!

Avoid this service provider at all cost!