How to cancel a SIM that I have never used

[MF3]

Hi, I was recently pressured by a pushy Virgin Media sales person who cold-called me when I was at a low ebb, suffering with anxiety and depression. She talked me in to taking out a package upgrade that is not suitable for me, despite me saying that I am already paying over the odds for just landline and broadband services. She signed me up for an O2 mobile phone SIM package. I didn't fully understand at the time what I was being forced to sign up for.
In the post I have received a Volt SIM from O2, however I haven't opened the envelope because I don't want this service from O2. I do not like pushy Virgin sales staff selling unsuitable and unwanted packages to vulnerable customers and I have made a complaint about this tactic.
How can I cancel my contract with O2? They have already taken a payment from me for a service which I didn't want and haven't used, and I would also like this to be refunded. As is the usual case in this modern age, being able to get the help you need is very difficult and most call centres are now based overseas. Thank you.

[madasaf1sh]

@MF3 

You will need to pay off the contract, and accept that Virgin will increase your monthly bill to cover any discounts applied and any boosts or extras maybe removed as well. 

Also it doesnt matter if you use it or not the sim comes activated on order, so just because you didnt use it is neither here or there, the payments are due... 

If you think you where missold by Virgin then you need to contact them on 0345 454 1111 or look at this link on how to lodge a complaint https://www.virginmedia.com/help/complaints

[MI5]

@MF3 

If within 14 days of receipt of sim you can return it and cancel for free.

https://www.o2.co.uk/help/phones-and-devices/returns-and-repairs/returning-your-device#changed-your-...

[MF3]

Thanks for your advice MI5.

[MF3]

Thank you very much for your reply madasaf1sh.

[Oxonian]

If you really were pushed to that extent @MF3, a 'phone call to your local Trading Standards might be justified. 👍