I am an existing 02 customer

[Lowsun10]

I have a dual capacity android phone and wish to keep my existing number, but to add another number to my system, what deals do you have on offer at the moment as the market is quite competitive. 

[Bambino]

@Lowsun10 This is not O2. This is a customer community. Click on the Shop link at the top of the page to find sim only offers or click on the link below:

How to find help & contact O2: A Guide - O2 Community

[jonsie]

Use USwitch

https://www.uswitch.com/mobiles/compare/sim_only_deals/o2/

Choose the deal you want

This will automatically redirect you to the O2 website

Just follow the prompts 

[Oxonian]

If I was in your position @Lowsun10, I would not get a second O2 SIM for my dual-SIM handset. 

In order to ensure that I had coverage in areas in which the O2 signal might be congested, I would be inclined to consider procuring a second SIM on a different network. 👍