How do I cancel a sim only contract if I lost the sim many years ago and don’t know the number?

[ColJack2050]

A good few years ago ( might be 7 or 8, I don’t remember exactly when ), I thought I was changing my contract to a sim only plan but ended up with a new SIM card, contract and number. 
I meant to get my existing number ported over but never got round to it. 
I barely used the new sim for a few weeks before going back to my original one and it has long since vanished into the void. 
I realised the other week that I’m still paying some £40ish a month for something that I don’t use. 
I don’t expect that I will get any of that money back and consider it a procrastination tax. 
The question is how do I go about getting that plan and sim and number cancelled if I don’t remember any of the details? 
I’ve never received any bills or anything in the post and as far as I can see, not recently had an email or text from Three that isn’t to do with my “proper” contract.  
The only info I have about it is the number used for the direct debit every month. 

[JonathanB]

Hi @ColJack2050,

Hopefully you managed to get through to the team from one of the other suggestions. There's one other solution I can think of. If you have a Three store nearby pop in with your photo ID, and they'll track down the account. They can't cancel it, but they can then give you a replacement SIM which will help you then pass security with the chat or phone teams.

Thanks,
Jonathan

[onthehorizon]

Contact customer services by live chat, or phone 0333 338 1001 and they will assist.

[ColJack2050]

I tried live chat and couldn’t get past the robot because I don’t have the number.. 🤷🏻‍♂️😂🤦🏼‍♂️

[PeteG]

If you enter a contact number instead, the system will let you pass through after 3 attempts with that number. 

Pete.

[ColJack2050]

Thank you, I’ll try that.