You haven't given much information, but I'll advise based on a few assumptions.
Assuming you are NOT currently VM customers, the addresses and mailboxes should have been deleted 90 days after service ended, in accordance with VM's terms and conditions. However, they frequently fail to do so and leave former customers at risk of being hacked and their financial and personal details stolen, their friends and family spammed. (I do wonder daily what the ICO would think about this lack of care and protection?)
Assuming the 90 days has passed, and the mailboxes are still valid, only VM can delete them now.
A member of the Forum Team (VM employees) will visit this post to confirm, then will take your details by private message. They will raise a ticket with the email provisioning team to get them deleted. Depending on workload it can be a few hours/days for them to reach this post.
If any of my assumptions are wrong, please advise and we'll go from there. Best wishes.
Welcome to the community forums and thank you very much for your post. We would be more than happy to assist with this further, before we do so can you confirm if the email accounts are still active and you have access to them? Also as mentioned previously are you no longer a VM account holder and left us more than 90 days ago?