I need to change my new number that I’ve just activated my new sim back to my old number

[Messiah]

I have just received a new sim to which I've activated and used , is there anyway that I can use my old number instead 

[Messiah]

I can't reply to any emails that gets sent to me this is the reason why I need my old phone number to get into my online accounts

[caesarome]

@Messiah 

Just put the other sim in your new device and call Sky on 150 to cancel this new one you have activated.

[Messiah]

I only have the new sim , my other sim is in my other iPhone that I have lost 

[caesarome]

If the lost iphone was from Sky then you need to report it to them so they can block it. Even if it isn't from Sky you would still need to get in touch so they can send you a replacement sim for the one that you have lost in the iphone.