Unable to change telephone number on my iPhone.

[Guildhall+man]

I've recently switched my mobile to sky, my number was also transferred. 
it has been working ok but I've just received a message from my phone saying that my FaceTime and iMessage will expire in 4 days. They are locked into my phone using a different telephone number, this was the number that came with the sim Sky supplied. I'm unable to change it on my phone. Any ideas anybody. 

is there a number I can ring at sky to talk with somebody?

[PandJ2020]

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@Guildhall+man wrote:

is there a number I can ring at sky to talk with somebody?

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150 from a Sky SIM.  But this isn't really a Sky Mobile issue - it's a configuration issue on your Apple account.

The answers you need are from Apple, e.g. https://support.apple.com/en-gb/108758