Connecting my Apple Watch to my O2 mobile phone contract

[KRW25]

Hi I’m struggling to connect my Apple Watch to my O2 iPhone contract it keeps coming up error when I try it on my watch. Would it be easier if I went into an O2 shop for them to do it on their system. 
Any help would be appreciated cheers 

[Enlli]

@O2Sarah- Can you help?

[O2Sarah-]

Thanks for the tag @Enlli 

@KRW25 I will send you a private message to see if we can get this working 😊